Preheat the oven to 350℉. Line a 9-inch springform pan with parchment paper. (For a rustic look, it’s okay to push and scrunch the paper into place and secure it with clips. Otherwise, you can cut parchment paper to size for the bottom and sides.)

To make the crumb top, mix the dry ingredients and then use your fingers to rub in the butter until the mixture resembles pea-sized lumps. Set aside.

For the cake, whisk all the dry ingredients together in a large bowl. 

With a stand mixer, whisk on high, the eggs, sugar, and vanilla until very thick. After about 3 minutes you should see a ribbon of beaten eggs trail back into the bowl when the whisk is lifted. Add the sour cream. 

Pour the egg mixture into the bowl of dry ingredients, add the blueberries, and fold together until blended. 

Spoon the batter into the prepared pan. Gently press the crumb top onto the batter. 

Bake for 25-30 minutes or until golden brown around the edges and a toothpick inserted comes out clean. Cool in the pan on a wire rack. Serve warm.