flour, baking powder and salt. Set aside. Cream butter and gradually beat in sugar. Add egg and milk and beat until smooth. Add dry ingredients. Dust blueberries lightly with flour. Fold into batter. Spread into greased and floured 9 inch square baking pan. To prepare topping: mix together sugar, flour and cinnamon. Cut in butter and mix into coarse crumbs. Sprinkle crumb mixture over cake batter. Bake at 375 for 40 45 minutes.