Preheat Oven: Preheat the oven to 350°F (175°C). Spray a large 6-tin muffin pan or a 12-tin standard size cupcake pan with nonstick baking spray.

Prepare Mashed Bananas: In a small bowl, mash the ripe bananas using a fork or potato masher. Set aside.

Mix Wet Ingredients: In a mixing bowl, combine sugar and melted butter. Mix for about 3 minutes until well combined. Add eggs one at a time, mixing well after each addition. Mix in vanilla extract and mashed bananas.

Incorporate Dry Ingredients: Add gluten-free all-purpose baking flour, baking powder, cinnamon, baking soda, and kosher salt to the wet ingredients. Mix until just combined. Fold in chopped walnuts if using.

Fill Muffin Tins: Divide the muffin batter evenly among the prepared muffin tins, filling each about 3/4 full.

Bake: Place the muffin pan in the preheated oven and bake for 25-35 minutes, or until a toothpick inserted into the center of a muffin comes out clean.

Cool and Enjoy: Once baked, remove the muffins from the oven and let them cool in the pan for a few minutes before transferring them to a wire rack to cool completely. Enjoy the muffins once cooled.