Preheat the oven to 375°F (190°C). Lightly grease or line 10 muffin cups with paper liners.

Mix flour, baking soda, baking powder, and salt together in a large bowl.

In a separate bowl, beat bananas, white sugar, melted butter, and egg together.

Stir the banana mixture into the flour mixture just until combined.

Spoon batter into prepared muffin cups, filling each about 3/4 full.

For the crumb topping, mix brown sugar, flour, and cinnamon together in a small bowl. Use a fork to incorporate 1 tablespoon of butter until crumbly.

Sprinkle crumb topping over muffins and bake in the preheated oven for 18 to 20 minutes, or until a toothpick inserted into the center comes out clean.