Preheat Oven at 350 °F (177 °C), grease and line muffin pans.
Prepare 2 level cups of oat flour. To get level cups, spoon out flour into the cup; when the cup is full, take the back of a knife and level off the top to reach the top of the measuring cup and not over the cup's rim.
In a medium-size bowl, mix oat flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
Add bananas, egg, milk, melted butter, honey or sugar, and vanilla extract to your blender; blend until smooth and creamy for about 1 minute.
Using a large bowl, pour your mixture from the blender into the bowl.
Slowly add dry ingredients to wet ingredients, using a hand whisk, gently fold in all the dry ingredients. Ensure it is fully combined.
Using an ice cream scoop, pour out muffin batter into the muffin pans. Bake for 15-20 minutes.
Use a toothpick to test the muffin to ensure they are fully baked. Place the toothpick in the center of the muffins. Once it comes out clean, please remove them from the oven and allow them to cool on a baking rack.
If you use honey instead of sugar, you should get about 15 muffins, If you use sugar, you should get 21 muffins. Serve at room temperature.