8 tablespoons unsalted butter, room temperature
1 cup all purpose flour
1/2 cup cornmeal
2 teaspoons baking powder
1/2 teaspoon table salt
1 cup sugar
2 large eggs
1/4 teaspoon vanilla extract
1/4 teaspoon freshly grated lemon zest (we used orange zest)
1/3 cup sour cream
2 cups blueberries, rinsed and patted dry

Streusel:

1/2 cup sugar
6 tablespoons all-purpose flour
2 tablespoons cornmeal
1/4 teaspoon ground cinnamon
pinch of table salt
2 tablespoons unsalted butter, cut into small pieces