Preheat oven to 375 and grease/line a muffin tray.
In a large mixing bowl, combine the 1 1/2 cups flour, baking soda, baking powder, and salt.
In a separate bowl, beat together the bananas, sugar, egg, and melted butter.
Stir the banana mixture into the flour mixture, just until moistened.
Spoon batter into muffin cups, about 2/3 full.
In a small bowl, combine the brown sugar, 2 tbsp. flour, and cinnamon. Cut in the 1 tbsp. butter using a pastry blender or two forks, until crumbly.
Sprinkle topping evenly on top of muffins.
Place tray in preheated oven and bake about 18 minutes, or until toothpick comes out clean once inserted in center.
Remove from oven and allow to cool 2-3 minutes before removing muffins from tray.