Preheat oven to 350ºF (177ºC). Grease two 9-inch round cake pans; dust lightly with flour and set aside. In a medium bowl, stir together flour, baking powder, and salt. In bowl of a stand mixer, beat granulated sugar and butter on low speed until well blended, scraping the sides of the bowl as needed. Increase speed to medium and beat 2 minutes until fluffy and well mixed. Reduce speed to low and add eggs one at a time, beating well after each addition. In a measuring cup, combine milk and vanilla. With mixer at low speed, add flour mixture alternately with milk mixture, beginning and ending with flour mixture, scraping bowl as needed until batter is smooth. Divide batter evenly between the two prepared pans. With hands, press crumb topping into large chunks and sprinkle evenly over batter. Bake 40-45 minutes until toothpick inserted into centers of cakes comes out clean. Cool cakes in pans on wire racks for 15 minutes. Loosen sides of cake from pans with small metal spatula or knife then invert each cake onto a plate, remove pans, and invert again onto write rack. Allow to cool completely, slice and serve.