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Rhubarb Crumb Cake

This Rhubarb Crumb Cake is tender, moist, and bursting with fresh rhubarb zing and a buttery crumb topping—perfect for dessert or breakfast!
Prep Time20 minutes
Cook Time50 minutes
Total Time1 hour 10 minutes
Course: Dessert
Cuisine: American
Keyword: Crumb Topping, Easy, Rhubarb, Seasonal
Servings: 8 servings

Ingredients

For the Crumb Topping:

  • 2/3 cup granulated sugar
  • 1/3 cup dark brown sugar
  • 1/2 teaspoon ground cinnamon
  • 1/4 teaspoon ground ginger
  • pinch salt
  • 8 tablespoons unsalted butter melted and still warm
  • 1 cup cake flour
  • 1 cup small-diced rhubarb
  • 2 tablespoons granulated sugar for rhubarb layer
  • 1 teaspoon cornstarch
  • 1/4 teaspoon ground ginger for rhubarb layer
  • 2 teaspoons all-purpose flour for rhubarb layer

For the Cake:

  • 1 cup cake flour
  • 1/2 cup granulated sugar
  • 1/4 teaspoon baking soda
  • 1/4 teaspoon table salt
  • 6 tablespoons unsalted butter cut into 6 pieces, softened but still cool
  • 1 egg egg
  • 1 egg yolk egg yolk
  • 1 teaspoon vanilla extract
  • 1/3 cup buttermilk
  • Powdered sugar for dusting

Instructions

Step 1: Prepare the crumb topping

  • In a medium bowl, whisk together 2/3 cup granulated sugar, 1/3 cup dark brown sugar, 1/2 teaspoon cinnamon, 1/4 teaspoon ground ginger, and a pinch of salt. Stir in 1 cup cake flour until combined. Slowly pour in the 8 tablespoons melted butter and mix until the mixture resembles coarse crumbs. Set aside.

Step 2: Prepare the rhubarb layer

  • In a separate bowl, toss the diced rhubarb with 2 tablespoons sugar, 1 teaspoon cornstarch, 1/4 teaspoon ground ginger, and 2 teaspoons all-purpose flour. This will help thicken the rhubarb juices as it bakes. Set aside.

Step 3: Make the cake batter

  • In a large mixing bowl, sift together 1 cup cake flour, 1/2 cup granulated sugar, 1/4 teaspoon baking soda, and 1/4 teaspoon salt. Add the softened butter pieces and use a hand mixer or stand mixer to beat the mixture until it’s crumbly.

Step 4: Add wet ingredients

  • In a small bowl, whisk together the egg, egg yolk, vanilla extract, and buttermilk. Gradually add this mixture to the flour and butter crumbs, mixing on medium speed until the batter is smooth and well combined.

Step 5: Assemble the cake

  • Spread half of the cake batter evenly into the prepared baking pan. Carefully spoon the rhubarb mixture over the batter, distributing it evenly. Dollop the remaining batter on top of the rhubarb layer and gently spread it out without mixing the layers.

Step 6: Add the crumb topping

  • Sprinkle the crumb topping evenly over the top layer of batter. The crumb topping will bake into a golden, buttery crust.

Step 7: Bake

  • Preheat your oven to 350°F (175°C). Bake the cake for 45 to 50 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs. The top should be golden brown and crisp.

Step 8: Cool and serve

  • Allow the cake to cool in the pan for at least 20 minutes before dusting with powdered sugar. Serve warm or at room temperature. This cake pairs beautifully with a cup of tea or coffee, or even a scoop of vanilla ice cream on the side.

Equipment

  • 9-inch square baking pan
  • Mixing Bowls
  • Whisk
  • Spatula
  • Measuring Cups and Spoons
  • Electric mixer or hand whisk
  • Sharp Knife

Notes

  • Store leftover cake covered at room temperature up to 2 days or refrigerate up to 5 days for freshness.
  • Freeze wrapped tightly for up to 3 months; thaw overnight in refrigerator before serving.
  • Use all-purpose flour as a substitute for cake flour for a denser crumb.
  • Substitute buttermilk with milk plus lemon juice or vinegar if needed.
  • Don’t skip cornstarch in the rhubarb layer to prevent sogginess.