For the Topping:
½ cup light brown sugar
¼ teaspoon ground cinnamon
½ cup all-purpose flour
2 tablespoons granulated sugar
Pinch of salt
¼ cup unsalted butter, softened, cut into 8 pieces
For the Cake:
½ teaspoon grated lemon zest
½ teaspoon salt
1½ cups all-purpose flour
⅔ cup granulated sugar
1½ teaspoons baking powder
1½ teaspoons vanilla extract
2 eggs, at room temperature
4 cups (20 ounces) fresh blueberries
10 tablespoons unsalted butter, softened
1. Make the Topping: With an electric mixer, mix the flour, sugars, cinnamon, and salt on low speed until good mixed, about forty five seconds. Add the butter and continue to mix on low velocity except the blend resembles wet sand and no massive butter portions remain, about 2½ minutes. Switch to a small bowl and set aside.
2. Make the Cake: adjust oven rack to scale down-center function and preheat oven to 350 levels F. Grease a circular 9-inch cake pan, line the backside of the pan with parchment, grease the parchment, then flour the within of the pan.
3. In a small bowl, whisk collectively the flour and baking powder; set aside. Utilising an electrical mixer, cream collectively the butter, sugar, salt and lemon zest at medium-excessive pace unless light and fluffy, about three minutes, scraping down the sides of the bowl as wanted. Add the vanilla and beat except combined, about 30 seconds. Scale back the mixer velocity to medium, then add eggs one after the other; beat for five to 10 seconds, then scrape down bowl and proceed to beat unless fully integrated (combination will appear damaged). Slash the mixer speed to low, then regularly add the flour combo and beat unless the flour is close to thoroughly included, about 20 seconds. Use a rubber spatula to conclude mixing until no flour pockets remain (the batter shall be very heavy and thick). Using the rubber spatula, gently fold blueberries into the batter until evenly allotted.
Four. Switch batter to ready pan; use an offset spatula to softly spread the batter evenly to the pan edges and tender the outside. Squeeze a handful of the streusel for your hand to kind a enormous cohesive clump; ruin up the clump with your fingers and sprinkle evenly over batter. Repeat with ultimate streusel.
5. Bake unless the highest is deep golden brown and a thin knife inserted into center of the cake comes out easy, about 55 minutes. Position on a wire rack for 20 minutes (the cake will fall reasonably because it cools).
6. Run a skinny knife around the facets of cake. Invert the cake, then peel off the parchment from the bottom of the cake and discard. Flip the cake correct-aspect-up onto a cooling rack or serving dish. Enable to cool for no less than 1 hour. Serve warm or at room temperature. Leftovers may also be saved at room temperature, in an airtight container or wrapped in plastic wrap, for up to 2 days.