You will need:
6 tablespoons (3/4 sticks) unsalted butter, at room temperature
3/4 cups sugar
2 extra-large eggs, at room temperature
¾ tsp vanilla extract
½ cup sour cream
1/8 cup milk
1 1/4 cups all-purpose flour
1 tsp baking powder
¼ tsp baking soda
¼ tsp kosher salt
½ pint (1 cup) fresh blueberries
Preheat the oven to 350F. Prepare an 8-inch x 2 inch round baking pan by greasing it and dusting it with flour.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and sugar until light and fluffy, about 5 minutes. With the mixer on low speed, add the eggs 1 at a time, then add the vanilla, sour cream, and milk.
In a separate bowl, sift together the flour, baking powder, baking soda, and salt. With the mixer on low speed add the flour mixture to the batter and beat until just mixed. Fold in the blueberries with a spatula and be sure the batter is completely mixed.
Transfer batter to prepared pan. Bake for 30 mins until a cake tester comes out clean. Cool in pan for 10 minutes, then turn onto a rack to cool completely.