Preheat oven to 200C.
Mix flour, salt and baking powder in a bowl.
Cream the butter and sugar with an electric whisk.
Beat the eggs and mash in banana with a fork.
Mix egg and butter mixtures with electric whisk.
Add flour and stir to combine.
Butter the sides of a loaf tin and pour in the mixture.
Bake for 45 minutes, or until a toothpick comes out clean