Rhubarb Elderflower Cake with Jam Glaze

Slice the cake while it’s still warm and you’ll wreck it. So don’t. Wait two hours instead.

Why You’ll Love This Elderflower Cake

Homemade rhubarb elderflower cake sounds fancy but it’s genuinely easy—the batter takes maybe 10 minutes if you don’t overthink the meringue. Two layers, jam in the middle, glaze on top. That’s the whole move.

Tastes light. Not dense. The separated eggs make it almost fluffy, which sounds impossible when you see rhubarb involved, but the jam stays on the layer, not soaking through everything.

Elderflower syrup does something weird—sharpens the rhubarb without making it sour. Lemon helps too.

The glaze sets but stays soft. Doesn’t crack when you cut into it.

What You Need for Rhubarb Elderflower Cake

Flour. All-purpose, sifted. About three-quarters cup plus a tablespoon. Why sift? Lumps kill the texture.

Baking powder. A little under two and a quarter teaspoons. Mix it with the flour right away.

Salt. Just a quarter teaspoon. Sounds dumb. Matters.

Eggs. Three large ones, separated. Room temperature. Cold eggs don’t whip right. Warm them five minutes in hot water if you forgot.

Sugar. You’ll use it twice—55 grams mixed into the yolks with cream and elderflower, then 45 grams beaten into the whites. Have it measured before you start.

Heavy cream. Half a cup plus a tablespoon. Thirty-five percent fat. Coconut milk works if you need non-dairy but the cake tastes different—still good, just heavier.

Elderflower syrup. A tablespoon in the batter. Another two tablespoons for the glaze. Nothing else tastes like this. Don’t skip it.

Gelatin. One teaspoon, or agar agar powder if vegan—use a little more, about a teaspoon and a half.

Rhubarb. Fresh or frozen. Diced. About two and a half cups. Frozen works fine—thaw it first, drain the liquid or the jam gets watery.

Lemon juice. One tablespoon plus a teaspoon. Cuts through sweet. Elderflower without it tastes flat.

Powdered sugar. Three-quarters cup for the glaze. Sifted helps but not essential.

Edible flowers. Optional. Looks nice but taste-wise? Doesn’t change anything.

How to Make Rhubarb Elderflower Cake

Heat the oven to 180 Celsius, which is 350 Fahrenheit. Put the rack in the middle. Line a 20-centimeter springform pan with parchment paper on the bottom only—no butter, no flour. The parchment keeps the crust tender.

Sift the flour, baking powder, and salt into a bowl. Sifting spreads the leavening evenly. Lumps will mess up the crumb.

In a second bowl, whisk the egg yolks with 55 grams of sugar until thick and pale. Add the cream and elderflower syrup. Keep whisking until totally smooth. This takes maybe a minute. The sugar needs to dissolve into the cream or the batter feels grainy.

Fold the dry ingredients into the yolk mixture using a rubber spatula. Fold slowly. Vigorous stirring breaks the structure you’re about to build with meringue.

Get a third, completely clean bowl—no grease, no yolk traces. Beat the egg whites until they’re foamy. Then gradually add the remaining 45 grams of sugar while you keep beating. Beat until stiff peaks form. The whites should be shiny and firm, standing straight up when you lift the beater. Don’t overbeat or they’ll separate and look dry and grainy.

Take a quarter of the meringue and fold it into the batter. This loosens the batter so the remaining meringue doesn’t deflate when it goes in. Then fold in the rest of the whites gently but thoroughly—no lumps visible, no white streaks, but also no vigorous stirring. A light hand keeps the air pockets trapped. That’s what makes the cake light.

Pour the batter into the pan. Smooth the top gently with an offset spatula.

Bake for 28 to 33 minutes. Start checking at 28. Insert a toothpick in the center—it should come out clean or with just a few moist crumbs. The top will be pale golden and just starting to pull from the edges. If it looks wet in the middle, give it another minute or two. Don’t overbake. Overbaking dries the cake out completely.

Cool on a rack completely. This takes between an hour and a half to two hours. Don’t skip this. Cooling pulls moisture out of the cake naturally. If you assemble while it’s warm, the jam and glaze will make it soggy.

Once it’s completely cool, run a thin knife around the edges to loosen it from the pan. Pop the springform latch. Slide the cake carefully onto a plate or cake board.

How to Make Rhubarb Jam and Get the Glaze Right

Sprinkle the gelatin over cold water—a tablespoon of water, one teaspoon of gelatin. Let it sit for five to six minutes. The gelatin blooms, absorbing the water. If you’re using agar agar instead, add it after the rhubarb is cooked and still hot, then simmer for two more minutes.

Put the diced rhubarb, 150 grams of sugar, and the lemon juice into a saucepan. Bring it to a gentle boil over medium heat. Then lower the heat and simmer for 12 to 15 minutes. Stir often so nothing sticks to the bottom and burns. The rhubarb will break down into soft pieces and the whole thing will look like syrup. The smell changes from sharp and acidic to something mellower and tart-sweet. That’s when you know it’s done.

Pull it off the heat. Stir in the bloomed gelatin until it dissolves completely. If you’re using agar, sprinkle it in and whisk it, then simmer for two minutes.

Pour the jam into a bowl. Cover it loosely and let it cool to room temperature. Then refrigerate for at least an hour. It needs to be cold and set but still spreadable—not a rock, not a liquid.

For the glaze, mix powdered sugar with the elderflower syrup—that’s two tablespoons of syrup and three-quarters cup of sugar. Stir until it’s smooth and opaque. It should drip slowly off a spoon but hold its shape. If it’s too thick, add a little water. If it’s too runny, add a bit more powdered sugar. There’s no exact ratio because the syrup has moisture in it already.

Rhubarb Elderflower Cake Tips and Common Mistakes

Egg whites need zero yolk in them. One tiny drop of yolk and they won’t whip properly—the fat breaks the bubbles. Use stainless steel or copper bowls if you have them. Plastic sometimes holds grease residue you can’t see.

The cake cracks sometimes. If that happens next time, lower the oven temp by 10 degrees or rotate the pan halfway through baking. Both help even browning without stress fractures.

The jam is too runny? Simmer it longer. Or add a tiny bit more gelatin next time—another quarter teaspoon. But honestly, a runnier jam tastes better because it spreads easier.

No elderflower syrup? Honey works. Or make simple syrup and add lemon zest to it. The flavor won’t be the same but it’ll still taste good.

Glaze too thick means add water a teaspoon at a time until it flows right. Too runny means powdered sugar, a little bit at a time.

Do not skip chilling the jam. Warm jam makes the cake layers slide sideways or soak the bottom layer. Patience here actually matters.

Handling the cake while it’s still warm breaks the crumb structure. Let it cool. All the way.

Leftover jam is incredible swirled into yogurt or spread on toast the next day. Honestly better than the cake sometimes.

Using frozen rhubarb is fine. Thaw it first and drain off the liquid that pools. Too much liquid in the jam makes the whole thing runny and then you’re simmering forever.

Cream and elderflower in the batter add moisture but be careful not to add too much or the batter deflates and the cake goes dense. Stick to the amounts listed.

Rhubarb Elderflower Cake with Jam Glaze

By Emma

Prep:

40 min

Cook:

35 min

Total:

1h 15min

Servings:

12 servings

Ingredients

• 120 g all-purpose flour, sifted (about 3/4 cup plus 1 tbsp)
• 11 ml baking powder (about 2 1/4 tsp)
• 1 ml salt (1/4 tsp)
• 3 large eggs, separated and at room temperature
• 100 g granulated sugar (just under 1/2 cup plus 1 tbsp), divided
• 130 ml heavy cream 35% (about 1/2 plus 1 tbsp cup), can sub coconut milk for non-dairy
• 15 ml elderflower syrup (1 tbsp), plus extra for glaze
• 5 ml powdered gelatin (1 tsp), or 8 ml agar agar powder for vegan
• 15 ml cold water (1 tbsp)
• 300 g fresh or frozen rhubarb, diced (about 2 1/2 cups)
• 150 g granulated sugar (3/4 cup plus 1 tbsp)
• 20 ml fresh lemon juice (about 1 tbsp plus 1 tsp)
• 100 g powdered sugar (3/4 cup) for glaze
• 30 ml elderflower syrup (2 tbsp) for glaze
• Optional edible flowers for garnish

Method

1. Cake
2. 1 Set oven rack mid-position. Heat oven to 180 C (350 F). Line 20 cm springform pan base with parchment only; no butter. Flour avoided here to keep crust tender; trust parchment.
3. 2 Sift flour, baking powder, salt together. Dry ingredients separate for even distribution; no lumps.
4. 3 Whisk egg yolks with 55 g sugar, cream, elderflower syrup till totally smooth. Don't rush here; sugar dissolves into cream for silkiness.
5. 4 Gently fold dry mix into yolk blend. Use rubber spatula; no vigorous stirring. Clumps kill lightness.
6. 5 In clean, dry bowl beat egg whites till foamy then gradually add remaining sugar (45 g) until stiff peaks form. Look for shiny, firm white peaks standing tall; over-beating dries whites, under-beating deflates.
7. 6 Fold a quarter of meringue into batter to loosen it. Then fold remaining whites gently but thoroughly, no lumps, no tough spots. A light hand keeps air trapped, making cake springy.
8. 7 Pour batter into pan. Smooth top gently with offset spatula.
9. 8 Bake 28–33 minutes. Start checking at 28 min. Toothpick inserted should come out clean or with a few moist crumbs. Top will be pale golden, edges just pulling from pan. Don’t overbake or cake turns dry.
10. 9 Cool on rack completely, 1 1/2 to 2 hours. Cooling important; warm cake drags moisture out from jam and glaze later.
11. 10 Remove from pan carefully by running knife around edges. Slide cake off parchment onto plate or cake board.
12. Rhubarb Jam
13. 11 Sprinkle gelatin over cold water; let bloom 5–6 minutes. Gelatin powder, not sheets, preferred for ease. Agar agar works but add once rhubarb is done and hot.
14. 12 In saucepan, combine rhubarb, sugar, lemon juice. Bring to gentle boil, then simmer medium heat 12–15 min until rhubarb breaks down and mixture thickens like syrup. Stir often to prevent sticking or burning. Aroma changes from sharp to mellow tart-sweet when ready.
15. 13 Remove from heat. Stir in gelatin till fully dissolved. Agar: sprinkle and whisk in, then simmer 2 more min.
16. 14 Pour jam into bowl; cover loosely, cool to room temperature. Refrigerate at least 1 hour till cold and set but spreadable, not rock solid.
17. Assembly
18. 15 Slice cake horizontally into two equal layers using serrated knife. Go slow; cake crumb fragile.
19. 16 Place bottom layer on serving plate. Spread chilled rhubarb jam evenly – don’t overload or cake will slide off.
20. 17 Set top layer gently over jam. Press lightly to attach but don’t squash airiness.
21. Elderflower Glaze
22. 18 Mix powdered sugar and elderflower syrup until glaze is smooth, opaque, and slightly runny. Add syrup or sugar incrementally. Should drip slowly off spoon but hold shape.
23. 19 Pour over cake, letting glaze flow elegantly down sides. Use spatula for coverage or just a ladle drizzle. Imperfections add charm.
24. 20 Decorate with edible flowers if desired; adds visual pop and subtle fragrance.
25. 21 Chill cake under dome in fridge. Keeps freshness 3 days max. Glaze softens slightly on cake surface; avoid warm rooms.
26. 22 == Tips & Troubleshooting ==
27. 23 Egg whites shouldn’t have any yolk traces—fat kills volume. Use copper or stainless bowls, no plastic residues.
28. 24 If cake cracks, reduce oven temperature slightly next time or rotate pan halfway through bake.
29. 25 Rhubarb jam too runny? Simmer longer or add little more gelatin next batch.
30. 26 No elderflower syrup? Substitute with honey or simple syrup infused with lemon zest, but flavor will shift.
31. 27 Glaze too thick? Thin with warmed water, little at a time. Too runny? Add more powdered sugar sparingly.
32. 28 Don’t skip chilling jam; warm jam makes layers slide or cake soggy quickly.
33. 29 Handling cake while still warm wrecks texture; patience pays off.
34. 30 Leftover jam is fantastic swirled into yogurt or spread on toast.
35. 31 Using frozen rhubarb? Thaw and drain excess liquid to avoid watery jam.
36. 32 Whisk cream and elderflower into batter adds moisture but be cautious – too much liquid deflates batter.

Nutritional information

Calories

310

Protein

6g

Carbs

42g

Fat

14g

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Frequently Asked Questions About Homemade Rhubarb Elderflower Cake

Can I make this cake the day before? Yeah. Bake it, cool it completely, assemble the next morning. The cake actually tastes better after sitting overnight because the flavors flatten out a bit and taste more balanced. The jam stays set if you keep it in the fridge.

What if the rhubarb jam doesn’t set? It probably needs more time in the fridge or you didn’t simmer it long enough. If it’s still runny after two hours of chilling, pour it back into the saucepan and simmer for another five minutes, add a tiny bit more gelatin, let it cool again. Should work the second time.

Can I use frozen rhubarb for this easy elderflower cake? Totally. Thaw it first though and drain the liquid that comes out. Frozen rhubarb releases more water than fresh, and that makes the jam runny if you’re not careful.

How long does the cake with rhubarb jam keep? Three days max in the fridge under a dome or loose cover. The glaze softens as it sits, which is good—it means it doesn’t crack when you cut into it. After three days the elderflower flavor fades and the glaze gets tacky.

What’s the difference between powdered gelatin and sheets? Powdered is easier. You just sprinkle it in. Sheets need blooming in cold water, then you squeeze them and add them. Both work. I use powder because I forget to buy sheets.

Can I make this cake without the elderflower syrup? Not really. It’s the whole point. If you absolutely can’t find it, honey with lemon zest gets you close but the light fluffy cake tastes like a basic vanilla cake then. You might as well make something else.