A delicious, rich and buttery rhubarb custard cake, with a crumb base and topping and a custardy cake layer in between. It can be made with fresh or frozen rhubarb.

Rhubarb custard cake sliced on serving board.

If you want to use up your garden or freezer rhubarb, this rhubarb cake uses 4 cups of rhubarb and bakes into a delicious sweet rhubarb treat.

Ingredients and substitutions

A few notes about the key ingredients …

Rhubarb – You can start with either fresh or frozen rhubarb for this cake. If using frozen rhubarb, as there is so much of it, it will slow the baking time, so be sure to bake the cake until it is domed, set and golden on top, which will be longer than the time to bake when using fresh rhubarb.

How to make this rhubarb custard cake

Dry ingredients for the crumb in a bowl.
1
Cold butter added to the crumb mixture.
2
Egg added to the crumb mixture.
3
  1. Start by mixing together the dry ingredients for the crumb mixture.
  2. Add the cold, cubed butter to the bowl and rub into the dry mixture with your fingers or a pastry cutter until the butter is in pea-sized pieces.
  3. Add the egg to the mixture and stir in until the mixture is crumbly. Set aside 1 cup of the crumb to use for the topping.
Most of the crumb mixture added to prepared baking pan.
4
Crumb mixture pressed into the baking pan.
5
Mixing the dry ingredients for the filling.
6
  1. Add the remaining crumb mixture to the prepared 9×9-inch baking pan.
  2. Press the mixture into the bottom of the pan and set aside.
  3. Start the filling layer by whisking together the dry ingredients.
Adding softened butter to the dry ingredients for the filling.
7
Adding eggs to the filling mixture.
8
Filling mixture mixed together in bowl.
9
  1. Add the softened butter to the dry mixture and use a fork to press the butter into the dry mixture until crumbly.
  2. Add the eggs to the mixture and stir in.
  3. Beat the mixture well with a fork until smooth.
Filling mixture after adding rhubarb.
10
Filling mixture added to the baking pan.
11
Remaining crumb mixture spooned on top of the rhubarb custard cake before baking.
12
  1. Add the rhubarb to the filling mixture and stir together well.
  2. Add the filling mixture to the baking pan and spread out evenly.
  3. Top with the reserved crumb mixture and bake.

Recipe tips!

  • Baking time will be extended when using frozen rhubarb, so be sure to bake the cake as long as needed. A tester might not come out completely clean, but the cake should feel set when inserting the tester and not liquidy.
  • If you don’t have a 9-inch square baking pan, use a 9 or 10-inch round springform pan instead. an 8-inch square baking pan may also work, though it will produce a taller cake which will require longer baking time. Baking time may differ with different-sized pans and between metal and glass pans.
Rhubarb custard cake sliced on serving board.

Storing and freezing

Store the cake at room temperature for up to 24 hours. After that, you can refrigerate it to extend the life a few more days.

You can also freeze the baked cake well-wrapped for up to 3 months.

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Rhubarb custard cake sliced on serving board.

Get the Recipe: Rhubarb Custard Cake

A delicious and unique rhubarb cake, with a crumb base and topping and a custardy cake layer in between. It can be made with fresh or frozen rhubarb.
5 stars from 1 rating
Prep Time: 20 minutes
Cook Time: 35 minutes
Total Time: 55 minutes
Yield: 9 servings

Ingredients

For the crumb mixture:

  • 2 cups all-purpose flour, spooned and levelled
  • 1/4 teaspoon salt
  • 1 teaspoon baking powder
  • 1/4 cup white granulated sugar
  • 2 teaspoons cinnamon
  • 1/2 cup butter, cold and cut into pieces
  • 1 large egg, beaten

For the filling:

  • 1 1/2 cups white granulated sugar
  • 1/2 cup all-purpose flour, spooned and levelled
  • 1/2 cup butter, softened
  • 2 large eggs
  • 1/2 teaspoon vanilla
  • 4 cups rhubarb, fresh or frozen, diced

Instructions
 

  • Preheat oven to 350F (non-convection). If using a glass pan, reduce the oven temperature to 325F.
  • Prepare a 9-inch square baking pan by greasing and lining the bottom and two sides with parchment paper, allowing the sides of the parchment to extend past the edge of the pan to use as handles to remove the cake later. Set aside. *See notes for other baking pan options.
  • In a medium bowl, whisk together the flour, baking powder, salt, sugar and cinnamon. Add the cold butter pieces and use your fingertips or a pastry cut to rub or cut the butter into the flour mixture until the butter pieces are no larger than pea-sized. Add the beaten egg to the mixture and use a fork to moisten the mixture with the egg until you have a lightly crumbly mixture.
  • Remove 1 cup of the crumb mixture and set aside for the topping. Add the remaining crumb mixture to the prepared pan and press it evenly into the bottom of the pan. Set aside.
  • Make the filling mixture by whisking together the sugar and flour in a large bowl. Add the softened butter to the bowl and use a fork to press the softened butter into the flour and sugar mixture until it is evenly moistened. Add the eggs and vanilla and stir in with the fork, then use a spoon to stir the mixture vigorously until smooth. Add the rhubarb and fold into the batter.
  • Spoon the batter into the baking pan on top of the base. Spread out evenly in the pan. Top with the reserved crumb mixture.
  • Bake the cake until it is set, domed and golden on top. A tester inserted in the centre of the cake will be mostly clean. The cake should feel set when inserting the tester and not be liquidy. If using fresh rhubarb, baking time is 30-40 minutes. For frozen rhubarb, baking time may be 45-55 minutes.
  • Remove cake from the oven and allow to cool in the pan. Lift the cake out of the pan using the parchment paper and cut into 9 slices for serving.
  • Store the baked cake at room temperature for up to 24 hours. You can refrigerate for an additional 2-3 days or freeze, well-wrapped, for up to 3 months.

Notes

If you don’t have a 9-inch square baking pan, use a 9 or 10-inch round springform pan instead. an 8-inch square baking pan may also work, though it will produce a taller cake which will require longer baking time. Baking time may differ with different-sized pans and between metal and glass pans.
Be sure to read the notes above this Recipe Card for more tips on making this recipe.
Cuisine: American, Canadian
Course: Dessert
Serving: 1serving, Calories: 494kcal, Carbohydrates: 68g, Protein: 6g, Fat: 23g, Saturated Fat: 14g, Polyunsaturated Fat: 1g, Monounsaturated Fat: 6g, Trans Fat: 1g, Cholesterol: 116mg, Sodium: 254mg, Potassium: 270mg, Fiber: 2g, Sugar: 40g, Vitamin A: 777IU, Vitamin C: 4mg, Calcium: 91mg, Iron: 2mg
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