01 -
Preheat the oven to 350°F. In a mixing bowl, beat the butter and sugar together until light and fluffy, about 6-7 minutes. Add the vanilla, lemon zest, and lemon juice, mixing to combine. Incorporate the eggs one at a time, mixing just until blended.
02 -
In a separate bowl, combine the flour and baking powder. Place the blueberries in a small bowl, sprinkle with a couple tablespoons of the dry ingredients, and stir gently to coat.
03 -
Add half of the dry ingredients to the butter mixture and stir to combine. Add the sour cream and mix again. Incorporate the remaining dry ingredients, mixing just until combined.
04 -
Gently fold the coated blueberries into the batter and pour it into a greased 8-inch square pan.
05 -
In the same small bowl that held the berries, combine the flour and sugar for the topping. Add the melted butter and mix lightly with a fork to form crumbs. Sprinkle the topping evenly over the batter in the pan.
06 -
Bake in the preheated oven for 40-45 minutes, or until a toothpick inserted into the center comes out clean or with moist crumbs. Allow to cool before slicing.