Heat oven to 350 degrees F. Butter and flour a 9 or 10-inch springform baking pan.
Sift flour, baking powder, and salt together in a medium bowl.
In a separate large bowl cream butter and sugar together until light and fluffy, about 3 minutes on medium speed. On low speed add eggs and vanilla, beating until fully incorporated
Add 1/4 of flour mixture, alternating with milk, beating each addition until fully incorporated, starting and ending with the flour mixture. Gently fold in blueberries. Batter will be thick. Make the streusel topping.
Pour batter into prepared pan; sprinkle streusel topping over cake. Bake until cake tester comes out batter-free, 60 to 70 minutes. Cool on wire rack 10 minutes. Remove from pan; cool for about 15 minutes before serving. Serve warm or cooled.
Streusel
In a medium bowl, combine flour, sugar, cinnamon, and salt. Using a pastry blender or fork, cut in the butter until fine crumbs form.
Using hands, squeeze together most of the mixture to form large clumps.