In lg bowl, mix the 1 1/2 flour, baking soda, baking powder, and salt. Mix bananas, sugar, egg and butter, then stir into dry mixture just until moistened. Fill muffin cups 3/4 full. Combine brown sugar, 1 tablespoon of flour, and cinnamon for the topping. Cut in butter until crumbly and sprinkle over muffins. Bake at 375° for about 20 minutes, until muffins test done.