INGREDIENTS
3 large ripe bananas, mashed
3/4 cup sugar
1 egg, slightly beaten
1/3 cup melted butter
1 teaspoon baking powder
1 teaspoon baking soda
1/2 teaspoon salt
1 1/2 cups flour

DIRECTIONS
Mash bananas.
Add sugar and slightly beaten egg.
Add melted butter.
Add the dry ingredients* and bake at 375 degrees for 20 minutes

fold in using a spatula roughly one turns, don't develops the gluten!
https://www.food.com/recipe/best-ever-banana-muffins-62286