Preheat the oven to 350°F (175°C) and grease a muffin tin or line it with muffin liners.

In a mixing bowl, combine the dry ingredients: flour, baking soda, baking powder, and salt.

In another bowl, mix the wet ingredients: mashed bananas, granulated sugar, brown sugar, melted butter, beaten egg, and vanilla extract until well combined.

Gradually add the dry ingredients to the wet mixture, stirring until just combined. Do not overmix.

Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.

Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.

Allow the muffins to cool in the tin for 5 minutes before transferring them to a wire rack to cool completely.