Preheat oven to 350F (not fan-assisted/convection) with rack in centre of oven.
Prepare an 8.5 x4.5-inch metal loaf pan by spraying with cooking spray, then lining the bottom and sides with a sheet of parchment paper.
In a large bowl, with a hand mixer, cream together the room temperature butter and sugar until light and fluffy, about 2-3 minutes.
Add the flour, baking powder, baking soda and salt and mix on low.
Add the eggs, one at a time, beating well between each addition.
Add the mashed bananas and mix until smooth.
Pour batter into prepared loaf pan and level top.
Bake in preheated oven for 45-55 minutes, or until a tester inserted in the centre comes out clean.
Remove from oven and allow to cool in the pan on a cooling rack for 10 minutes, then remove from the baking pan and allow to cool further on a baking rack.
