In large bowl, mix the flour,baking soda,baking powder,and salt. In seperate bowl Mix bananas, sugar, egg and butter. Stir Banana mix into dry mixture just until moistened.
Fill muffin cups 3/4 full. Combine Brown Sugar, Flour(for topping), and Cinnamon in a seperate bowl.
Cut in butter until crumbly. Sprinkle over muffins.
Bake at 375° for about 20 minutes, until muffins test done. Cool in pan for 10 minutes.