Preheat your oven to 350 degrees F. Line a standard muffin tin with paper liners or coat the cups with baking spray.
In a medium bowl, combine the flour, baking powder, baking soda, salt, and pecans.
In a large bowl, mash the bananas and then stir in the sugar.
Add the egg and mix well. Then stir in the melted butter gradually.
Dump the dry ingredients into the wet ingredients and stir until just combined. (Be sure to not over mix!)
Fill each muffin tin cup with muffin batter. Bake for 20 to 25 minutes. (see note)
The muffins are done when a toothpick comes out clean when inserted into the center. Remove the muffins to a wire rack to cool. Serve warm or at room temperature.
Notes
If you're using a large muffin tin, increase the baking time to 30-35 minutes, using the toothpick test to check for doneness. You will also have a smaller yield for this recipe if using a larger pan due to the increased size of the muffins.