Rhubarb Crumb Cake
May 05, 2025
This Rhubarb Crumb Cake is the perfect spring treat—bright, buttery, and impossible to resist. A rich, tender cake forms the base, swirled with tart and tangy rhubarb that brings a pop of seasonal flavor. It’s all finished with a buttery, crisp crumble topping that adds just the right amount of crunch. Whether you serve it for brunch, dessert, or sneak a bite straight from the pan, this is one of those cakes that keeps calling you back for just one more little piece.
Ingredients - Crumb Topping
½ cup (63g) all-purpose flour
¼ cup (50g) light brown sugar
¼ cup (23g) old-fashioned rolled oats
2 teaspoons dried sumac (or 1 teaspoon lemon zest as substitute)
Pinch of salt
¼ cup (55g) unsalted butter, very soft
Ingredients - Rhubarb Cake
1 lemon
¾ cup (150g) light brown sugar
2 large eggs
¾ cup (165g) sour cream
½ cup (113g) unsalted butter, melted
1 teaspoon vanilla bean paste or vanilla extract
½ teaspoon kosher salt
1¼ cups (160g) all-purpose flour
1½ teaspoons baking powder
½ teaspoon baking soda
1½ cups (150g) fresh or frozen chopped rhubarb, in ½-inch pieces
Instructions
Preheat your oven to 350°F (175°C). Butter or spray an 8-inch square baking pan and line it with a strip of parchment paper that hangs over two sides.
To make the crumb topping, combine the flour, brown sugar, oats, sumac, and salt in a small bowl. Add the soft butter and mix it in with your fingers until the mixture is evenly moistened and crumbly.
To make the cake batter, zest the lemon directly into a large bowl. Add the brown sugar and eggs, and whisk until pale and foamy, about 1 minute. Whisk in the sour cream, melted butter, vanilla, and salt until smooth.
Add the flour, baking powder, and baking soda to the bowl. Stir until just combined, then use a rubber spatula to fold gently for a few final strokes. The batter will be thick. Fold in the chopped rhubarb.
Pour the batter into the prepared pan and tap the pan gently on the counter to release any air bubbles. Smooth the top with an offset spatula. Sprinkle the crumb topping evenly over the batter.
Bake until the cake is puffed and golden and a tester inserted in the center comes out clean, 50 to 60 minutes. Let it cool in the pan on a rack for 15 minutes. Then lift the cake out using the parchment overhang and let it cool completely on the rack.
(Store the cake, well wrapped, at room temperature for up to two days.)
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