Set oven to 350°F. Grease the baking pan with butter, dust with some flour, and set aside.
Prepare the dry ingredients: In a bowl, whisk together the flour, baking powder, baking soda, and salt (if not using salted butter).
Mash together 4 large ripe bananas in a medium bowl and set them aside.
Prepare the wet ingredients: In another bowl, cream the sugar and butter until it's combined, then add the eggs one at a time whisking after each addition. Then stir in the vanilla extract. Don't over mix.
Combine: Add half of the dry ingredients into the wet ingredient. Fold to combine. Add the mashed bananas, fold to combine again. Then fold in the remaining dry ingredients.
Pour the batter into the prepared loaf pan. Sprinkle with nuts/seeds if desired.
Bake: Place in a 350°F preheated oven for 45 minutes or till a skewer inserted in the middle of the bread comes out clean.