Preheat oven to 375 degrees F (190 degrees C). Lightly grease 10 muffin cups or line with muffin papers.
Mix 1 1/2 cups flour, baking soda, baking powder, and salt in a large bowl. Beat bananas, sugar, egg, and melted butter in another bowl. Stir banana mixture into flour mixture just until moistened. Spoon batter into prepared muffin cups.
Combine brown sugar, 2 tablespoons flour, and cinnamon in a small bowl. Blend in 1 tablespoon butter until mixture resembles coarse cornmeal. Sprinkle topping over muffins.
Bake in preheated oven until golden and tops spring back when lightly pressed, 18 to 20 minutes.