Preheat your oven to 300°F (150°C) and grease two 9x5-inch loaf pans.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.

In a larger mixing bowl, cream together the butter and sugar until light and fluffy, then beat in the eggs one at a time.

Mix in the mashed bananas until fully blended.

Add the dry ingredients alternately with the buttermilk, being careful not to overmix.

Pour the batter evenly into the prepared loaf pans.

Bake in the preheated oven for approximately 1 hour, until golden brown.

Let cool in the pans for about 10 minutes before transferring to wire racks.