Here is my favorite rhubarb and custard layer cake recipe, with a soft sponge made with custard powder, a creamy custard buttercream frosting, and layers of tangy rhubarb jam.
This cake is the one I turn to when I want something a little different from the usual chocolate or vanilla. The custard powder gives it such a comforting flavor, and the rhubarb jam adds just the right amount of tartness. My kids always ask for extra frosting on their slices!
Why You’ll Love This Rhubarb and Custard Layer Cake
- Quick and easy – This cake comes together in under an hour, making it perfect for when you need an impressive dessert without spending all day in the kitchen.
- Nostalgic flavor combination – The classic pairing of tangy rhubarb and creamy custard brings back childhood memories while feeling special enough for any celebration.
- Simple ingredients – You probably have most of these pantry staples on hand already, and the rhubarb jam makes it accessible year-round without needing fresh rhubarb.
- Impressive presentation – The layers of cake, jam, and custard frosting look bakery-worthy, but the recipe is straightforward enough for home bakers of any skill level.
What Kind of Rhubarb Jam Should I Use?
For this cake, you can use store-bought rhubarb jam or make your own if you have fresh rhubarb on hand. If you’re buying it from the store, look for a jam that’s thick and spreadable rather than too runny, as this will help it stay put between your cake layers. Some rhubarb jams are mixed with strawberry, which actually works great in this recipe and adds a nice sweetness to balance the tartness. If you can only find rhubarb that’s a bit loose, you can simmer it on the stove for a few minutes to thicken it up before using it in your cake.
Options for Substitutions
This cake is pretty forgiving when it comes to swaps, so here are some options if you need them:
- Rhubarb jam: If you can’t find rhubarb jam, strawberry-rhubarb jam works great and is easier to find. You could also use strawberry jam on its own, though you’ll lose that tangy rhubarb flavor.
- Custard powder: This is the star of the show for that custard flavor, so I wouldn’t skip it. If you absolutely can’t find it, you can make a substitute by mixing 2 tablespoons cornstarch with 2 tablespoons vanilla pudding mix for every 50g called for, but the flavor won’t be quite the same.
- Self raising flour: Don’t have self raising flour? Make your own by adding 1½ teaspoons baking powder and ¼ teaspoon salt to 200g plain flour. Just remember the recipe already calls for baking powder and salt, so adjust accordingly.
- Caster sugar: Regular granulated sugar works fine here. If you want the finer texture of caster sugar, just pulse your granulated sugar in a food processor for a few seconds.
- Butter: You can use margarine or a baking spread instead, though butter gives the best flavor for the frosting.
Watch Out for These Mistakes While Baking
The biggest mistake when making layer cakes is not letting your cakes cool completely before assembling – warm cakes will melt the buttercream and turn your beautiful layers into a sliding mess, so give them at least 30 minutes to cool on a wire rack.
Overmixing the batter once you add the self-raising flour can lead to a tough, dense cake instead of a light and fluffy one, so mix just until the ingredients are combined and no flour streaks remain.
When it comes to the rhubarb jam layer, spreading it too close to the edges will cause it to squeeze out when you add the top layer, so leave about half an inch border around the edge.
Finally, make sure your buttercream is thick enough to support the weight of the top cake layer – if it’s too soft, pop it in the fridge for 10 minutes to firm up before assembling.
What to Serve With Rhubarb and Custard Layer Cake?
This cake is pretty rich and sweet on its own, so I like to keep things simple and serve it with a hot cup of tea or coffee – the slight bitterness really balances out the sweetness of the custard and rhubarb. A dollop of lightly whipped cream or vanilla ice cream on the side is always a good call if you want to make it extra special for dessert. You could also serve fresh berries like strawberries or raspberries alongside it, which pair beautifully with the tangy rhubarb flavor. For an afternoon tea situation, this cake works great cut into smaller squares and served on a platter with other treats.
Storage Instructions
Store: This cake keeps really well at room temperature in an airtight container for 2-3 days. If your kitchen is warm, you can pop it in the fridge for up to 5 days, though the texture might firm up a bit. Just let it sit out for 20 minutes before serving if you’ve refrigerated it.
Freeze: You can freeze individual slices wrapped tightly in plastic wrap and then in foil for up to 3 months. It’s great to have a slice ready when you need a sweet treat without making a whole cake.
Serve: Thaw frozen slices in the fridge overnight or at room temperature for about an hour. The custard buttercream and rhubarb jam layers taste best when the cake isn’t too cold, so give it a little time to warm up before digging in.
| Preparation Time | 20-30 minutes |
| Cooking Time | 15-20 minutes |
| Total Time | 35-50 minutes |
| Level of Difficulty | Easy |
| Servings | 8 slices |
Estimated Nutrition
Estimated nutrition for the whole recipe (without optional ingredients):
- Calories: 3150-3400
- Protein: 35-42 g
- Fat: 90-105 g
- Carbohydrates: 540-590 g
Ingredients
For the cake:
- 1.25 cups caster sugar (I use Domino Golden Sugar for better flavor)
- 4 eggs (room temperature, about 70°F)
- 1.5 cups self raising flour (I always use King Arthur for a consistent rise)
- 3.5 oz custard powder
- 1 tsp baking powder
- 3 tbsp milk
- 1/2 tsp salt
For the filling and topping:
- 5.5 oz icing sugar (sifted to remove lumps)
- 1.75 oz custard powder (I prefer Bird’s Custard Powder for the most authentic taste)
- 4.5 oz butter (softened to room temperature for a smoother frosting)
- 1 tbsp milk
- 1 tsp vanilla extract
- 10.5 oz rhubarb jam
Step 1: Prepare the Cake Batter and Bake
- 1.25 cups caster sugar
- 4 eggs
- 1.5 cups self-raising flour
- 3.5 oz custard powder
- 1 tsp baking powder
- 3 tbsp milk
- 1/2 tsp salt
Preheat your oven to 180°C (170°C fan/356°F) and grease two 8-inch round cake tins with butter or baking spray.
In a large mixing bowl, combine the room-temperature eggs, caster sugar, self-raising flour, 3.5 oz custard powder, baking powder, milk, and salt.
Beat with an electric mixer on medium speed for 2-3 minutes until the batter is smooth, pale, and well-combined—this aeration is crucial for a light, fluffy cake.
Divide the batter evenly between the prepared tins and smooth the tops.
Bake for 12-18 minutes until a toothpick inserted in the center comes out clean and the cakes are golden brown.
Step 2: Cool and Level the Cake Layers
Remove the cakes from the oven and let them cool in the tins for 5 minutes, then turn them out onto a wire cooling rack to cool completely.
Once fully cooled, use a serrated knife or cake leveler to gently slice off any domed tops—this creates flat, even surfaces for better assembly and a professional appearance.
I like to do this gently with a sawing motion rather than pressing down, which helps keep the crumb structure intact.
Step 3: Make the Custard Buttercream
- 5.5 oz icing sugar
- 1.75 oz custard powder
- 4.5 oz butter
- 1 tbsp milk
- 1 tsp vanilla extract
While the cakes cool, prepare the frosting by adding the softened butter, sifted icing sugar, and 1.75 oz custard powder to a clean mixing bowl.
Beat on medium speed for 3-4 minutes until the mixture is light, fluffy, and pale—this incorporates air and creates a smooth texture.
If the frosting seems too thick to spread, add the tablespoon of milk a little at a time, beating well between additions.
Finish by adding the vanilla extract and beat once more until fully incorporated.
Step 4: Assemble the Layer Cake
- custard buttercream from Step 3
- 10.5 oz rhubarb jam
- one cooled cake layer from Step 2
Place one cooled cake layer on your serving plate or cake stand.
Spread or pipe about half of the custard buttercream from Step 3 onto the top of the first layer in an even layer.
Stir the rhubarb jam gently to loosen it slightly, then spread it evenly over the buttercream layer.
I find that warming the jam very slightly (about 10 seconds in the microwave) makes it easier to spread smoothly without disturbing the frosting beneath.
Step 5: Finish and Serve
- second cooled cake layer from Step 2
- remaining custard buttercream from Step 3
- sifted icing sugar for dusting
Carefully place the second cooled cake layer on top of the jam, aligning it gently with the bottom layer.
Spread or pipe the remaining custard buttercream from Step 3 onto the top of the cake, creating a smooth or decorative finish as desired.
Dust the top generously with sifted icing sugar for a classic, elegant presentation.
Slice and serve immediately—the cake is best enjoyed fresh, though it will keep well covered at room temperature for up to 2 days.
Fluffy Rhubarb and Custard Layer Cake
Ingredients
For the cake
- 1.25 cups caster sugar (I use Domino Golden Sugar for better flavor)
- 4 eggs (room temperature, about 70°F)
- 1.5 cups self raising flour (I always use King Arthur for a consistent rise)
- 3.5 oz custard powder
- 1 tsp baking powder
- 3 tbsp milk
- 1/2 tsp salt
For the filling and topping
- 5.5 oz icing sugar (sifted to remove lumps)
- 1.75 oz custard powder (I prefer Bird's Custard Powder for the most authentic taste)
- 4.5 oz butter (softened to room temperature for a smoother frosting)
- 1 tbsp milk
- 1 tsp vanilla extract
- 10.5 oz rhubarb jam
Instructions
- Preheat your oven to 180°C (170°C fan/356°F) and grease two 8-inch round cake tins with butter or baking spray. In a large mixing bowl, combine the room-temperature eggs, caster sugar, self-raising flour, 3.5 oz custard powder, baking powder, milk, and salt. Beat with an electric mixer on medium speed for 2-3 minutes until the batter is smooth, pale, and well-combined—this aeration is crucial for a light, fluffy cake. Divide the batter evenly between the prepared tins and smooth the tops. Bake for 12-18 minutes until a toothpick inserted in the center comes out clean and the cakes are golden brown.
- Remove the cakes from the oven and let them cool in the tins for 5 minutes, then turn them out onto a wire cooling rack to cool completely. Once fully cooled, use a serrated knife or cake leveler to gently slice off any domed tops—this creates flat, even surfaces for better assembly and a professional appearance. I like to do this gently with a sawing motion rather than pressing down, which helps keep the crumb structure intact.
- While the cakes cool, prepare the frosting by adding the softened butter, sifted icing sugar, and 1.75 oz custard powder to a clean mixing bowl. Beat on medium speed for 3-4 minutes until the mixture is light, fluffy, and pale—this incorporates air and creates a smooth texture. If the frosting seems too thick to spread, add the tablespoon of milk a little at a time, beating well between additions. Finish by adding the vanilla extract and beat once more until fully incorporated.
- Place one cooled cake layer on your serving plate or cake stand. Spread or pipe about half of the custard buttercream from Step 3 onto the top of the first layer in an even layer. Stir the rhubarb jam gently to loosen it slightly, then spread it evenly over the buttercream layer. I find that warming the jam very slightly (about 10 seconds in the microwave) makes it easier to spread smoothly without disturbing the frosting beneath.
- Carefully place the second cooled cake layer on top of the jam, aligning it gently with the bottom layer. Spread or pipe the remaining custard buttercream from Step 3 onto the top of the cake, creating a smooth or decorative finish as desired. Dust the top generously with sifted icing sugar for a classic, elegant presentation. Slice and serve immediately—the cake is best enjoyed fresh, though it will keep well covered at room temperature for up to 2 days.
