Rhubarb Crumb Coffee Cake

For the Cake

1/3 cup sour cream

1 egg + 1 yolk

2 teaspoons vanilla

1 cup cake flour

1/2 cup granulated sugar

1/2 teaspoon baking soda

1/2 teaspoon baking powder

1/4 teaspoon salt

6 tablespoons unsalted butter, room temperature

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Rhubarb Filling

1/2 pound rhubarb, cut into 1/2 inch pieces

1/4 cup granulated sugar

2 teaspoons cornstarch

1 teaspoon Ginger, divided

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Crumb Topping

1/3 cup brown sugar

1/3 cup granulated sugar

1/8 teaspoon salt

1 stick (1/2 cup) unsalted butter, melted

1 teaspoon Cinnamon

1 cup cake flour

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1. Preheat oven to 325°F. Grease an 8-inch square baking pan. Set aside.

2. Make the cake: in the bowl whisk the sour cream, egg, egg yolk, and vanilla.

3. In the bowl of a stand mixer fitted with paddle attachment mix the flour, sugar, baking soda, baking powder, and salt. Then add in the butter and 1/4 of the sour cream. Mix until just combined. Then add in the remaining sour cream mixture in two batches, beating for 30 seconds after each addition. Set aside.

4. Make the rhubarb filling: in a bowl combine the rhubarb, sugar, cornstarch and 1/2 teaspoon Ginger. Set aside.

5. Assemble the cake: pour half the cake batter into the prepared pan. Top with the rhubarb filling, then spoon the remaining batter on top the rhubarb.

6. Make the crumb topping. In a bowl combine the sugars, salt, melted butter, Cinnamon and the remaining 1/2 teaspoon Ginger. Then stir in the flour until just combined. Using your fingers press the crumbs into 1/2 inch chunks to cover the cake.

7. Bake for 45-55 minutes or until a toothpick comes out clean. Cool completely on a wire rack before cutting.

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