Preheat oven to 350 degrees F (175 degrees C).
Coat muffin pans with non-stick spray, or use paper liners.
Add flour, baking powder, baking soda, and salt in a bowl, whisk to combine; set aside.
Combine bananas, sugar, egg, vanilla and melted butter in a large bowl. Fold in flour mixture, and mix until dry ingredients are just combined. Do not over mix (this will make your muffins tough). Scoop about 1/4 cup of batter each muffin tin.
Bake in preheated oven for 15-20 minutes. Muffins will spring back when lightly tapped.