Start by mixing the bananas, butter, sugar, egg, vanilla extract, baking soda, baking powder, ground cinnamon, flour together in a large mixing bowl.
Mix until smooth.
Fold in the walnuts
Spray your muffin tin, with non-stick cooking spray.
Spread your batter into the prepared pan, and place the tin into your air fryer basket. Set the temperature to 320 degrees, F for 12 minutes.
After 12 minutes my muffins were nice, if they are not, add an additional 2 minutes. Check. For doneness.
Plate, serve and enjoy!