Preheat oven to 350 degrees F
In a small bowl, whisk the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl mash the bananas, add the sugar, egg, vanilla and melted butter, mix to combine. Gently fold in flour mixture, and mix just until dry ingredients are combined. DO NOT over mix. Divide the muffin mix evenly into each muffin cup. About 1/4 cup of batter in each muffin tin. (I use an ice cream scoop)
Bake in preheated oven for 18-22 minutes.