Set your oven to 350°F (176°C). Position a rack in the center.

Line a 9x5-inch loaf pan with parchment paper, leaving overhang on the long sides for easy removal. Lightly grease any exposed surfaces.

In a large bowl, mash the bananas with a fork until mostly smooth. A few small lumps are fine and actually give better texture.

To the mashed bananas, add the melted butter, brown sugar, eggs, sourdough discard, sour cream, and vanilla extract. Whisk until smooth and well combined.

In a separate medium bowl, whisk together the flour, baking soda, baking powder, salt, and cinnamon (if using).

Add the dry ingredients to the wet ingredients. Use a spatula to fold gently until just combined. No dry streaks, but don't overmix. A few small lumps are fine.

If using chocolate chips, nuts, or other add-ins, fold them in now.

Pour the batter into the prepared loaf pan and smooth the top with the spatula.

Place the pan in the center of the oven. Bake for 55-65 minutes.

The bread is done when a toothpick inserted into the center comes out with just a few moist crumbs (not wet batter). The top should be deep golden brown and the internal temperature should read 200-205°F (93-96°C).

If the top is browning too quickly before the center is set, loosely tent with aluminum foil around the 40-minute mark.

Let the bread cool in the pan for 15 minutes.

Use the parchment overhang to lift the loaf onto a wire rack. Cool for at least another 15 minutes before slicing.

Preheat oven to 350°F (176°C) with rack in center position.

Pour batter into lined pan. Bake 55-65 minutes until toothpick comes out with moist crumbs.

If top is browning too fast, tent with foil at the 40-minute mark.

Cool in pan 15 minutes, then transfer to wire rack.

Fill liners ¾ full with batter.

Bake at 350°F (176°C) for 20-25 minutes until a toothpick comes out clean.