Preheat the oven to 350*. Grease a 9-inch spring form pan lightly with butter or vegetable oil.

Sift the flour, baking powder, and salt in a small bowl for the cake.

Cream the butter, sugar, and vanilla in a medium-size mixing bowl with an electric mixer on medium speed until the mixture is light and fluffy, about 2 minutes. Stop the mixer once or twice to scrape the bowl with a rubber spatula.

Add the eggs one at a time to the butter mixture and mix on medium speed after each addition until blended 8 to 10 seconds. Scrape the bowl each time.

Fold one-third of the dry ingredients in by hand until they have absorbed the liquid but are not thoroughly blended. Fold in half the milk by hand with several strokes, then the rest of the dry ingredients, folding just until they are absorbed. Add the rest of the milk and fold it until the batter is smooth.

Fold the blueberries in gently.

Pour the batter into the prepared pan. Bake the cake on the center oven rack until the top is set but not golden, 25 to 30 minutes.

Meanwhile, prepare the topping: Place all the ingredients in a food processor and pulse until blended about 10 pulses. Without a food processor, mix all the dry ingredients in a small bowl and rub the butter into the mixture with your fingers.

When the top of the cake is set, cover the surface with spoonfuls of topping and return the cake to the oven until the topping spreads and begins to get crunchy, 15 to 20 minutes.

Remove the cake from the oven and serve it hot.