Rhubarb Custard Cake

This delightful rhubarb custard cake is a light and delicious (EASY!) dessert…perfect served with a scoop of ice cream or dollop of whipped cream.

rhubarb custard cake on white plate with ice cream

I think rhubarb desserts deserve a little more credit. Rhubarb on its own? Um, no thanks. But something magical happens when rhubarb is combined with just the right thing. 

Strawberries. Brown Sugar. Warm Vanilla Sauce. Just to name a few.

And in today’s recipe, combining the tart fruit with a sweet custard cake might be the best thing that has ever happened to rhubarb. 

top down view of triangle piece of rhubarb custard cake on white plate

This rhubarb custard cake is unassuming in appearance (especially if your rhubarb is naughty and sinks while baking), but it more than makes up for that when you take your first bite:

Creamy + Sweet + Tart

An easy little cake

There is nothing difficult or time consuming about this cake. It comes together fast, and is a perfectly light spring or summer dessert. 

Even better, the batter needs to be whisked by hand. Don’t use an electric mixer or too much air will be incorporated into the batter which makes the rhubarb more likely to sink while baking.

mixing eggs and sugar together in glass bowl

You want to whisk the eggs and egg yolk and sugar until the color noticeably lightens and the mixture is thick, but it should only take 30-60 seconds. Don’t go too crazy here. 🙂

Follow up with the butter, lemon zest, and sour cream. 

And finally the dry ingredients. You can’t get much simpler than this. 

mixing sour cream, butter, eggs and lemon zest in small bowl

Mix until the batter is thick and smooth. 

I use a 9-inch round cake pan for this recipe. It also helps to chill the batter for 10-15 minutes before baking.

I pop it in the fridge while getting my rhubarb in order. 

swirl of vanilla cake batter in glass bowl

Let’s talk about rhubarb

I have literally no idea what variety of rhubarb is living its best life in the garden bed next to my house. Some stalks are green. Some are pinkish-red. Some are a combo. The plant is huge and unwieldy. And I love it.

For this cake, you want about 6-7 stalks of rhubarb (maybe 8- or so inches in length). 

I’m pretty sure any variety of rhubarb will do. 

stalks of rhubarb on wood cutting board

I like to choose smaller stalks of rhubarb. Leave those behemoth ones to chop up for strawberry rhubarb pie. 

Choosing thinner stalks of rhubarb will help the rhubarb stay perched on top while the cake bakes vs sinking to the bottom. 

If you only have thicker stalks, don’t panic, there’s a simple solution:

  • take a sharp knife and carefully slice the stalks in half lengthwise so they are thinner

slicing rhubarb stalk in half lengthwise

The only tricky part of this recipe

Spoiler alert: it’s actually not that tricky.

Arrange the rhubarb on top of the cake batter in whatever pattern your heart desires. Straight lines. That’s what my heart desires. 

Do NOT press or push the rhubarb into the cake batter. Like, not at all. Lay it on top very lightly.

Pressing the rhubarb into the cake batter, even the tiniest bit, may make it even more prone to sink while baking.

If you aren’t feeling long strips of rhubarb (it can get a bit stringy when cutting the baked cake), you can chop the rhubarb into bite-size pieces. 

baked and unbaked rhubarb custard cake

As you can see, I followed all the rules:

  • hand mixing the batter only
  • slicing thin stalks of rhubarb
  • not even pressing one tiny bit when adding the rhubarb to the top of the cake

And still. My rhubarb always sinks a little bit. I’ve made this cake several times…always some sinking. 

Even though it would be prettier if the rhubarb would mind its manners, I don’t stress about it.

The most important part is getting tart bites of rhubarb with the sweet, custardy cake, and that happens whether the rhubarb stays on top or not. 

baked rhubarb custard cake in 9-inch pan

The cake will puff and brown on the edges but stay pretty soft in the center. 

You don’t want it raw in the center, but don’t overbake it or else you’ll eliminate the custard texture that makes this cake so phenomenal. 

Also, another delightful surprise: the edges of the cake are absolutely amazing. Slightly more set up than the middle, they are golden and chewy, and so, so good. 

piece of rhubarb custard cake on white plate with ice cream and fork taking out a bite

It takes a phenomenal rhubarb recipe to really get me excited. And after making this rhubarb custard cake several times, it’s clear that it is a keeper. 

Brian says it’s one of his favorite desserts. No surprise, really, since he also says that about strawberry rhubarb anything whenever I make it. 

Tart and sweet, the contrasting flavors in this cake are incredible. With a scoop of vanilla ice cream? Unreal.

One Year Ago: Easy Moroccan Chicken Skewers with Crazy Good Green Sauce
Two Years Ago: Roasted Sweet Potato Lentil Salad 
Three Years Ago: Strawberry Rhubarb Pie 
Four Years Ago: Summer Roasted Vegetable Orzo Salad with Fresh Basil 
Five Years Ago: Little Lemonies {Yummy Lemon Brownies} 
Six Years Ago: No-Bake Dark Chocolate Granola Bites 
Seven Years Ago: Peanut Butter Cookie Dough Dip 
Eight Years Ago: Apple Stuffed Chicken Breasts 

Rhubarb Custard Cake

Yield: 8 servings
Prep Time: 20 minutes
Cook Time: 50 minutes
Total Time: 1 hour 10 minutes
half a piece of cake on white plate with ice cream

Ingredients

  • 2 large eggs
  • 1 large egg yolk
  • 1 1/4 cups (9.25 ounces) granulated sugar
  • 4 tablespoons (1/4 cup) butter, melted and cooled until just warm (I use salted)
  • 1/4 cup sour cream
  • 1-2 teaspoons fresh lemon zest (from about 1 lemon)
  • 1 cup (5 ounces) all-purpose flour
  • 3/4 teaspoon baking powder
  • 1/4 teaspoon salt
  • 10-12 ounces rhubarb stalks (about 6 small/medium stalks, 8 inches long)

Instructions

  1. Preheat the oven to 350 degrees F. Lightly grease a 9-inch round cake pan (you can line the bottom with a parchment circle, if desired).
  2. In a large bowl, whisk together the eggs, egg yolk, and sugar with a wire whisk (don't use a hand mixer - it will incorporate too much air for this cake) until pale and thick, 30 seconds to 1 minute.
  3. In a small bowl, stir together the melted butter, sour cream and lemon zest. Add to the egg mixture and whisk until combined.
  4. Add the flour, baking powder and salt. Mix with a rubber spatula until the batter is smooth. Spread evenly in the prepared pan. Chill the batter for 10 minutes.
  5. Make sure the rhubarb stalks are dried well. If they are over 1/4-inch thick, slice them carefully in half lengthwise. Cut the stalks to fit and arrange over the batter next to each other, covering as much of the batter as you can (but keeping the rhubarb in a single layer). DO NOT PRESS THE RHUBARB INTO THE CAKE BATTER. Lay it very gently on top without pressing at all or else it will be prone to sinking during baking (mine still does each time I make this, but it definitely sinks less if I haven't pressed the rhubarb at all into the cake).
  6. Bake the cake for 45-55 minutes until browned and puffed around the edges. The center may still be slightly soft set but it shouldn't be wet batter. Add additional time, if needed.
  7. Let the cake cool for 10 minutes (or completely) before slicing into pieces. Serve with a dollop of whipped cream or a scoop of ice cream. It's delicious warm, room temperature or chilled.

Notes

Rhubarb: using longer pieces of rhubarb makes for a prettier presentation, but it can be a little "stringy" cutting into the cake. Alternately, you can cut the rhubarb into bite-size pieces and scatter those over the top (don't press them into the batter!). They'll most likely sink while baking, but the combination of tart rhubarb in every bite and sweet custard cake is still super delicious. Also, I think you could definitely try other fruits in place of the rhubarb (raspberries or blueberries come to mind!).

Frozen Rhubarb: I haven't tried using frozen rhubarb in this recipe. My recommendation would be to probably thaw and pat dry before using.

Sinking Fruit: I've made this cake many times, and my rhubarb sinks to some degree every time. It doesn't affect taste at all, so I don't stress about it too much. A few factors that may help prevent sinking: don't overmix the sugar and eggs. It's really important to mix them until pale and thick for the custard texture (you'll notice the color lightening) but too much mixing will incorporate more air which contributes to the rhubarb sinking. Also, using thin stalks of rhubarb (or cutting them in half so they are thinner) will also help.

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Recipe Source: slightly adapted from this recipe (omitted rum, decreased sugar, added a few extra notes) – thanks to Melanie M. (a MKC reader who emailed me) for telling me about this recipe!