Preheat oven to 325°F (165°C). Grease a 9x5 loaf pan.
Combine flour, baking powder, sugar, salt and baking soda. Blend egg and buttermilk together, and add all at once to the flour mixture. Mix just until moistened. Stir in butter. Pour into prepared pan.
Bake for 65 to 70 minutes, or until a toothpick inserted in the bread comes out clean. Cool on a wire rack. Wrap in foil for several hours, or overnight, for best flavor.