This classic blueberry crumb cake recipe is easy to make and perfect for any occasion. The cake is moist and fluffy, with a sweet and tangy blueberry filling and a crunchy crumb topping. To make the cake, you'll need flour, sugar, baking powder, salt, butter, eggs, milk, vanilla extract, and fresh blueberries. Mix the dry ingredients together, then add the wet ingredients and mix until smooth. Fold in the blueberries and pour the batter into a greased baking dish. To make the crumb topping, mix flour, sugar, and butter until crumbly, then sprinkle over the cake batter. Bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean. Serve warm or at room temperature.