Topping:

1/2 C. flour

1/2 C. light brown sugar, packed

2 T. granulated sugar

1/4 tsp. cinnamon

pinch of salt

4 T. unsalted butter, softened but still cool, cut up into 8 pieces

 

Cake:

1-1/2 C. flour

1-1/2 tsp. baking powder

10 T. unsalted butter, softened but still cool

2/3 C. granulated sugar

1/2 tsp. salt

1/2 tsp. lemon zest

1-1/2 tsp. vanilla extract

2 eggs, room temperature

4 C. fresh blueberries

 

To make crumb topping, in standing mixer with flat beater, mix flour, sugars, cinnamon, and salt. Add cut-up butter and mix until it has a “wet sandy” texture. Pour topping into a separate bowl. Preheat oven to 350 degrees. Cut out a circle of parchment paper to line the bottom of a 9″ springform pan. Butter and flour the sides of the pan. Whisk together flour and baking powder in a separate bowl. In same standing mixer with flat beater, mix butter, sugar, salt, and lemon zest until light and fluffy (about 3 minutes). Scrape down bowl then beat in vanilla (about 30 seconds). Add eggs, one at a time, and scrape down the bowl. Batter will be loose. With mixer running at low speed, slowly add flour mixture. Beat until almost fully incorporated. With spatula, finish mixing, then gently fold in the blueberries. Transfer batter to pan; spread evenly using a spatula. To add topping, squeeze streusel mixture in hand, then crumble over batter in a even layer. Bake for about 55 minutes or until golden brown on top and a toothpick inserted in the center comes out clean. Cool and run a knife around the edge before removing from the pan.