Preheat the oven to 350℉. Line a muffin pan with paper liners and set aside.
In a medium bowl, mix together the flour, baking powder and baking soda.
In a separate bowl, cream together the bananas, sugar, egg and butter until smooth.
Slowly mix the dry ingredients into the wet ingredients until just combined.
Divide the batter evenly into the prepared muffin pan and bake in the preheated oven for 25 minutes, or until a toothpick inserted in the center of the muffin comes out clean.