Preheat oven 375*. Lightly grease 10 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 just until moistened. Spoon batter into prepared muffin cups.
In a small bowl mix together brown sugar, flour and cinnamon. Cut in 1 T butter until mixture resembles coarse cornmeal. Sprinkle on top over muffins. Bake in preheated oven for 18-20 minutes; until toothpick inserted comes out clean.