Preheat over to 350 F. Grease and flour 8" x 4" metal loaf pan. Set aside.
Sift together flour, baking powder, baking soda and salt. Set aside.
Cream the sugar and butter together until light. Stir in beaten egg. Add in smashed bananas and beat until combined.
Stir wet mixture into dry mixture in thirds, alternating with buttermilk. Stir until just combined. Do not over mix.
Pour mixture into prepared loaf pan. Bake for about an hour.
Let cool in pan, on wire rack, for 10 minutes. Remove from pan. Finish cooling on wire rack. Can be wrapped in aluminum foil and stored at room temperature for about a week. Can also be frozen for about a month.