Combine the flour, baking powder, baking soda, cinnamon and salt in a medium mixing bowl.
In a separate bowl, combine the mashed bananas, sugar, egg, vanilla and butter.
Mix together the wet and dry ingredients until incorporated, being careful not to over mix.
Place 1/4 cup of batter in each lined or sprayed muffin cup. Mix 1/4 cup of sugar and 1 1/2 teaspoons of cinnamon together in a bow. Sprinkle the mixture over the tops of the muffin batter. Swirl with a toothpick, if desired.
Bake at 350 degrees for 15-20 minutes until a toothpick inserted into the center of the muffin comes out clean. Enjoy!