Preheat oven to 375°F, prepare 10 muffin cups in a pan

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. Scoop batter into prepared muffin cups.

In a small bowl mix together brown sugar, 2 tablespoons of flour, and cinnamon. Cut in 1 tablespoon of butter until mixture resembles coarse cornmeal. Sprinkle over top of the muffins.

Bake in oven for 18 to 20 minutes, until a toothpick inserted into center of the muffin comes out clean.