Easy Rhubarb Custard Cake has a layer of creamy, tangy sweet custard below a fluffy yellow cake.

Magic Rhubarb Custard Cake

Our son has recently taken an interest in magic tricks, and he’s learned one card trick that has managed to baffle and impress us all.

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It involves several steps which don’t seem to follow any logic or reason, but somehow, to the delight and wonder of all of us, the correct card is always revealed in the end.

This Rhubarb Custard Cake is a magic trick of its own, made with the simplest ingredients and a few steps that will make little sense as you make it, but somehow always results in a fluffy cake with a gorgeous layer of tangy sweet rhubarb custard at the bottom. Magic.

Spatula holding a slice of rhubarb custard cake.

This recipe comes from the Amish Community Cookbook, a collection of recipes gathered from Amish and Mennonite cooks across the U.S. and Canada. It’s filled with other comfort foods I grew up with, like Amish Apple Fry Pies, Amish Chicken and Noodles, and the best Homemade Amish White Bread, but this Rhubarb Custard Cake was one I had never heard of or tried before.

Of course, I knew I could trust the Mennonites to deliver a delicious cake with little fuss. It might surprise you to find a cake mix recipe in an Amish cookbook, but sometimes Amish families need shortcuts just as much (or more!) than the rest of us.

Pink plate with a slice of rhubarb custard cake.

Here’s Why We Love this Rhubarb Cream Cake

It’s so fast! You can have this in the oven in about 15 minutes.
It uses simple (and few) ingredients. If you can get your hands on some rhubarb, you likely already have the rest of the ingredients on hand!
It’s so moist. The spoonable custard is rich and creamy, almost like a thick glaze for the cake.
It’s great for potlucks and family reunions. This fluffy, golden cake will be a hit at any gathering. The bright, tangy sweetness of rhubarb is a nice break from the usual brownies and chocolate chip cookies!

Key Ingredients

Yellow cake mix, eggs, sugar, oil, cream, and chopped rhubarb in bowls on a pink background.

Rhubarb – You’ll need 4 cups of chopped rhubarb, which is about 4-5 large stalks.
Sugar – Granulated sugar balances out the tangy rhubarb.
Yellow cake mix (plus the ingredients to make it) – Most call for some combination of vegetable oil, eggs, and water.
Heavy whipping cream- You’ll need 1 ¾ cups of cream to pour over the cake.

How to Make Old Fashioned Rhubarb Custard Cake

Before we dive in, let me just say this. Making this cake is going to feel wrong. When you start pouring cream over the top of the cake batter, an internal alarm is going to start ringing in your head.

Just this once, I’m going to tell you to ignore your baking instincts. This really works, I promise!

Granulated sugar coating chopped rhubarb in a pretty bowl with pink edges.

Egg and oil being stirred into yellow cake mix.

Preheat the oven to 350 degrees. Grease and lightly flour a 9 x 13 inch cake pan.
Prep the rhubarb. Place the rhubarb in a bowl and sprinkle sugar over top, giving it a stir to coat. Allow the mixture to sit while you prepare the other ingredients.
Prep the cake. Prepare the cake mix according to package instructions then pour the batter into the prepared pan.
Add rhubarb and cream. Sprinkle the rhubarb and sugar mixture evenly over the top of the cake. There will be some sugary liquid at the bottom that you’ll want to add too. Pour the cream over the entire top.
Place the cake in the oven and bake for 45-55 minutes, or until the top is golden brown and set and a toothpick comes out clean (the bottom third of the cake will still be wet so don’t base the toothpick test on that portion).
Serve warm or chill for neater slices. You can serve this cake warm, but you’ll need a spoon! The custard will be runny (but so delicious) when warm. If you give the cake a few hours to chill in the fridge it will set up into neat slices.

Make Ahead and Storage Instructions

This rhubarb custard cake actually benefits from some chilling time, so feel free to make it up to 24 hours in advance. The cake can be stored, covered, in the fridge and will keep for 3-4 days.

You can serve the cake cold or allow it to come to room temperature before serving. You can even warm it up in the microwave. We love it both warm and cold!

Spatula holding a slice of rhubarb cream cake.

FAQs

Can I use frozen rhubarb?

You can! You don’t even have to thaw it! Just follow the instructions as usual, breaking up any rhubarb pieces that are stuck together before tossing them with the sugar.

Can I use other fruits?

I personally haven’t tried this with other fruits, but some readers have subbed half the rhubarb for strawberries or blueberries with great success. I recommend reducing the sugar by about a ¼ cup if you’re using other sweeter fruits.

Can I freeze rhubarb cream cake?

I don’t recommend freezing this cake, as the custard layer might break when thawed.

What does rhubarb taste like in a cake?

Rhubarb has a very tangy, puckery flavor that benefits from a good bit of sugar. I like to think of it as nature’s Warhead. Give fresh rhubarb a whiff and you’ll see what I mean–it hits you immediately with an earthy, tangy fresh smell.

In cakes like this one and our Rhubarb Upside Down Cake, the rhubarb is combined with sugar and cake batter to create a sweet cake with just a hint of tang.

Should rhubarb be cooked before baking?

No, you don’t need to cook the rhubarb before baking the cake.

Should you soak rhubarb before baking?

All you need to do is rinse, chop, and sprinkle sugar on the rhubarb before baking.

Fork holding a single bite of rhubarb custard cake beside a slice of cake on a pink plate.

More Rhubarb Recipes

Can’t get enough of that tangy sweet flavor? Here are a few more of our favorite rhubarb recipes!