Preheat the oven to 325°F (160°C). Grease a 9x5-inch loaf pan. Alternatively, line it with parchment paper and lightly grease the lining and any exposed parts of the inside of the pan.
In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
In a large bowl, whisk together the melted butter, oil, brown sugar, and granulated sugar until smooth. Add the eggs, sour cream, and vanilla extract, and whisk until well combined.
Stir in the mashed bananas until evenly incorporated.
Gently fold the flour mixture into the wet ingredients, mixing until just combined. (Be careful not to over-mix the batter; a few lumps are fine.)
Pour the batter into the prepared loaf pan and smooth the top. Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Allow the banana bread to cool in the pan for 10 minutes, then remove it from the pan and place it onto a wire rack to cool completely.
Notes
Store tightly wrapped in an airtight container at room temperature up to 3 days.
For tips, step-by-step photos, and extra details, be sure to read the full post above before starting. It’s packed with helpful info to answer common questions!