Preheat the oven to 350°F. Grease a muffin tin with cooking spray or line with 12 paper liners.
In a medium sized mixing bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon. Set aside.
In a separate large mixing bowl, whisk together the mashed bananas and melted butter. Add an egg, granulated sugar, packed light brown sugar, and vanilla extract. Whisk together until all ingredients are well incorporated.
Add the dry ingredients to the wet. Fold in using a rubber spatula until just combined and no big lumps of flour remain.
Fill muffin cups until 3/4 full. Bake in the preheated oven for 25-30 minutes or until a toothpick inserted in the center comes out clean.
Remove from the oven and let cool in the muffin tin for 5-10 minutes. Then, remove from the tin and let cool completely on a cooling rack. Enjoy!