Preheat oven to 325 degrees.
Line a baking sheet with parchment paper.
Mix the dry ingredients (flour, sugar, baking soda, salt) in a bowl.
Combine the wet ingredients (mashed bananas, egg, melted butter) in another bowl.
Pour wet ingredients into dry ingredients and mix thoroughly.
Drop 3-tablespoon portions of the dough onto the baking sheet lined with parchment paper.
Bake in the preheated oven about 15-20 minutes until the cookies are golden brown and the edges are set.