1Preheat over to 375 degrees. Lightly grease 10-12 muffin cups. In a large bowl, mix together flour, baking soda, baking powder, and salt. In another bowl, beat together bananas, sugar, egg, and melted butter. Stir the banana mixture into the flour mixture until moistened. Spoon batter into prepared muffin cups. In a small bowl, mix together brown sugar flour and cinnamon. Cut in butter until mixture resembles a coarse cornmeal. Sprinkle topping over muffins. Bake for 18-20 minutes, until a toothpick inserted into center of a muffin comes out clean.