Prep the pan and oven: Heat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with a parchment sling for easy removal.

Whisk dry ingredients: In a medium bowl, whisk flour, baking soda, baking powder, salt, and cinnamon until evenly combined. Set aside.

Mash the bananas: In a large bowl, mash the bananas until mostly smooth with a few small lumps. You should have about 1 1/2 cups.

Mix the wet ingredients: To the bananas, add granulated sugar, brown sugar, melted butter, oil, sour cream, vanilla, and eggs. Whisk until glossy and well combined.

Combine gently: Add the dry ingredients to the wet. Use a spatula to fold until just combined. Stop mixing when you no longer see dry streaks. A few small lumps are fine.

Fold in add-ins: If using nuts or chocolate, fold them in now. Don’t overmix.

Pan it up: Scrape the batter into the prepared loaf pan. For a bakery look, sprinkle the top with turbinado sugar or lay a peeled banana sliced lengthwise on top, cut side up.

Bake: Bake at 350°F (175°C) for 55–70 minutes, depending on your oven. It’s done when a toothpick comes out with a few moist crumbs but no wet batter. Tent loosely with foil after 45 minutes if the top is browning too fast.

Cool properly: Let the bread cool in the pan for 15 minutes, then lift it out and cool on a rack for at least 1 hour before slicing. This sets the crumb so it stays moist and slices cleanly.

Serve: Slice thick and enjoy warm or at room temperature. A pat of salted butter or a smear of cream cheese is lovely.