1/2cup (1 stick)unsalted butterroom temperature, plus more for the pan
2cupsall purpose flourplus more for the pan
1 1/2tspbaking powder
1/2tspsalt
3/4cupsugar
1largeegg
1tsppure vanilla extract
1/2cupmilk
5cups (2 pints)wild or cultivated blueberries
Streusel Topping
1cupflour
1/4cuppacked light brown sugar
1tspground cinnamon
1/4tspsalt
6Tbspunsalted butterroom temperature
Instructions
Streusel Topping
In a medium bowl, combine the flour, sugar, cinnamon and salt. Using a pastry blender or fork, cut in the butter until fine crumbs form.
Using your hands, squeeze together most of the mixture to form large clumps.
Cake
Heat oven to 350°F. Butter a springform baking pan and dust with flour, tapping out the excess. Set aside.
In a medium bowl, sift together the flour, baking powder and salt; set aside.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and sugar on medium speed until light and fluffy, about 3 minutes. Reduce mixer speed to low, and add the egg and vanilla, beating until fully combined.
Add the reserved flour mixture, alternating with the milk, a little of each at a time, starting and ending with the flour mixture. Remove from mixer. Gently fold in the blueberries.
Pour the batter into the prepared pan; sprinkle the streusel topping over the cake.
Bake until a cake tester comes out batter-free, 60-70 minutes.
Transfer to a wire rack to cool for 10 minutes. Remove from pan; cool for 15 minutes before serving.
Notes
The streusel topping can be frozen in an airtight container for up to 6 months.