In a mixing bowl, cream butter and sugar. Beat in eggs, milk and vanilla. Combine flour and baking powder; add to creamed mixture just until combined. Gently fold in blueberries. Pour into a greased 9-in. x 5-in. x 3-in. loaf pan. Combine sugar and cinnamon; sprinkle over top. Bake at 350 degrees F for 50-55 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack to cool completely.