Crumb Topping:

·     Nonstick cooking spray, for the pan

·     1 cup chopped walnuts

·     1/4 cup sugar

·     1 teaspoon ground cinnamon

Batter:

·     1/2 cup (1 stick) unsalted butter, at roomtemperature

·     1 1/2 cups sugar

·     2 large eggs, at room temperature

·     1 teaspoon vanilla paste

·     1 cup sour cream, at room temperature, plusadditional for serving

·     2 cups all-purpose flour

·     1 teaspoon baking powder

·     1 teaspoon baking soda

·     1/4 teaspoon kosher salt

1. For the crumb topping: Preheat the oven to 350degrees F. Spray a 9-inch springform pan with nonstick cooking spray.

2. In a medium bowl, combine the walnuts, sugar andcinnamon. Set aside.

3. For the batter: In the bowl of a stand mixerfitted with the paddle attachment, beat the butter and sugar on medium speeduntil fluffy, 3 to 5 minutes. Add the eggs, one at a time, to the buttermixture, allowing each to be fully incorporated. Add the vanilla paste and sourcream and beat until smooth.

4. Combine the flour, baking powder, baking sodaand salt in a large bowl. Add to the batter and mix until combined.

5. Spread the batter in the prepared springform panand sprinkle with the crumb topping. Bake until a cake tester inserted in thecenter of the cake comes out clean, about 45 minutes. Place the cake, still inthe pan, on a wire rack and let cool to room temperature. Remove from the pan,then slice and serve with a dollop of sour cream if desired.