Combine the flour, salt, baking soda, cinnamon and nutmeg and set aside. In a bowl, whisk the egg and add brown sugar, mixing until smooth. Stir in the vanilla extract. Add sour cream and melted butter and mix until a smooth batter forms. Stir in the dry ingredients, then add mashed bananas and mix until the batter comes together. The batter will be thick. Using an ice cream scoop or 1/4 cup measure, scoop batter into the liners. Bake for 15-18 minutes. Let cool completely before frosting