Preheat the oven to 425℉ (220℃). This is the trick to getting your muffins to rinse! Grease a 12-cup muffin pan or line cups with resuable (or paper) liners.
In one bowl, combine gluten-free flour, baking powder, baking soda, salt and cinnamon and set aside.
In a separate bowl, mix together mashed bananas, brown sugar, egg, vanilla and melted butter until well combined.
Slowly fold in the flour mixture and mix with a wooden spoon until smooth.
Spoon batter into the prepared muffin pan, filling each one until they are almost full (leaving a small amount of space from the top)
Place the muffin pan into the oven and cook for 5 minutes. Then, reduce the oven to 350℉ (175℃) and cook for an additional 10 minutes.
Cool briefly in the muffin tin, then transfer to a wire rack to cool completely. Enjoy!