Preheat oven to 350F (not fan-assisted/convection) with rack in centre of oven. *Reduce oven temperature by 25F for glass pans.
Prepare an 8.5 x4.5-inch metal loaf pan (at least 2 1/2 inches deep) by spraying with cooking spray, then lining the bottom and sides with a sheet of parchment paper that extends about 1-inch over the sides, to use as handles to remove the loaf after baking. Set aside.
In a medium bowl, whisk together well the flour, baking powder, baking soda and salt. Set aside.
In a large bowl with an electric mixer or the bowl of a stand mixer fitted with the paddle attachment, cream together the room temperature butter and sugar until the mixture is light and fluffy, about 2-3 minutes.
Add the eggs, one at a time, beating well between each addition and scraping down the sides and bottom of the bowl as needed.
With mixer on low, add the flour mixture, alternately with the mashed bananas (add 1/3 flour mixture, then 1/2 the bananas, then more flour, then remaining banana, ending with the remaining flour). Mix until well combined, then give it a quick, 15-second beat.
Pour batter into prepared 8x4-inch loaf pan and level top.
Bake in preheated oven for 45-55 minutes, or until a tester inserted in the centre comes out clean. *Start checking the loaf at about 40 minutes. If the top is still quite pale, no need to test. Start testing when the top is cracked and turning golden.
Remove from oven and allow to cool in the pan on a cooling rack for 10 minutes, then remove from the baking pan, gently remove the parchment paper and allow to cool further or completely on a baking rack.
Recipe can be doubled and divided between and baked in two 8x4 loaf pans.Loaf will keep well, tightly wrapped and stored at room temperature for several days. The loaf can also be frozen up to 2 months.Be sure to read the “Ingredient and Cook's Notes" (above the recipe card!), where I share more detailedtips, variations and substitution suggestions for this recipe!