Blueberry happiness

Blueberry Coffee Cake 

Source: Cook's Illustrated

Makes one 9-inch cake, serving 8 to 10

Streusel

1/2 cup unbleached all-purpose flour (2 1/2 ounces)
1/2 cup packed light brown sugar (3 1/2 ounces)
2 tablespoons granulated sugar
1/4 teaspoon ground cinnamon
pinch table salt
4 tablespoons unsalted butter (1/2 stick), cut into 8 pieces, softened but still cool

Cake

1 1/2 cups unbleached all-purpose flour ( 7 1/2 ounces)
1 1/2 teaspoons baking powder
10 tablespoons unsalted butter (1 1/4 stick), softened but still cool
2/3 cup granulated sugar (about 4 3/4 ounces)
1/2 teaspoon table salt
1/2 teaspoon grated lemon zest
1 1/2 teaspoons vanilla extract
2 large eggs , room temperature
4 cups fresh blueberries (about 20 ounces), picked over

For the streusel: In standing mixer fitted with flat beater, combine flour, sugars, cinnamon, and salt on low speed until well combined and no large brown sugar lumps remain, about 45 seconds. Add butter and mix on low until mixture resembles wet sand and no large butter pieces remain, about 2 1/2 minutes. Transfer streusel to small bowl and set aside.

For the cake: Adjust oven rack to lower-middle position; heat oven to 350 degrees. Spray 9-inch round cake pan with 2-inch sides with nonstick cooking spray, line bottom with parchment or waxed paper round, and spray round; dust pan with flour and knock out excess. 

In a small bowl, whisk the flour and baking powder together then set aside.  In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, sugar, salt and lemon zest at medium speed until light and fluffy, about 3-4 minutes, stopping to scrape down the sides of the bowl as necessary.  Beat in the vanilla.  Add the eggs, one at a time, beating well after each addition.  With the mixer on low, gradually add the flour mixture, beating until just about incorporated.  Remove the bowl from the mixer and use a rubber spatula to finish stirring - the batter will be very thick.  Gently fold in the blueberries. 

Transfer the batter to the prepared pan; spread in an even layer.  To top with the streusel - pick up a handful of streusel and squeeze to form a clump.  Break this large clump into smaller pieces and sprinkle over the batter.  Continue until you've used all of the streusel.  Bake for about 55 minutes, or until the streusel is golden brown and a toothpick inserted in the center comes out clean.  Transfer pan to a wire rack and cool for 15-20 minutes.  Run a thin knife around the edges of the cake then invert it onto the rack.  Remove the parchment then turn the cake streusel side up and let cool on the wire rack.