Preheat the oven to 350 degrees F with the rack in the middle of the oven. Butter an 8 1/2 x 4 1/2 - inch loaf pan, set aside.
In a bowl whisk together the flour, baking powder, baking soda, cinnamon, and salt.
In a stand mixer fitted with the paddle attachment, cream the butter, sugar and brown sugar on medium speed for about 3 minutes. Add the eggs one at a time and mix well after each. Mix in the vanilla and heavy cream.
Remove the bowl from the mixer and use a rubber spatula to stir, alternate adding the dry ingredients and the mashed bananas in 3 batches, mixing just enough to combine them. Add the nuts and mix just to combine.
Pour the batter into the prepared pan and smooth out the top. Bake for about 1 hour or until a tester comes out clean. If the top is over browning after 45 minutes, gently drape the top with foil.