Prep the pan and oven: Heat oven to 350°F (175°C). Line a 9x5-inch loaf pan with parchment and lightly grease it. This prevents sticking and helps you lift the loaf out cleanly.

Mash the bananas: In a large bowl, mash the bananas until mostly smooth with a few small lumps. You want about 1 1/4 to 1 1/2 cups.

Whisk in the wet ingredients: Add peanut butter, oil (or melted butter), eggs, brown sugar, and vanilla. Whisk until well combined and glossy. If your peanut butter is very thick, warm it slightly so it mixes easily.

Combine the dry ingredients: In a separate bowl, whisk the gluten-free flour, baking soda, baking powder, salt, and cinnamon. This evenly distributes the leavening agents.

Bring it together: Add the dry ingredients to the wet. Stir with a spatula until just combined. Don’t overmix—stop when you no longer see dry streaks. Fold in chocolate chips or nuts if using.

Fill the pan: Scrape the batter into the prepared pan and smooth the top. For extra peanut flavor, drizzle 1 to 2 tablespoons of warmed peanut butter over the surface and swirl with a knife. Sprinkle a pinch of flaky salt if you like.

Bake: Bake 55 to 65 minutes, or until the top is set and a toothpick comes out with a few moist crumbs (not wet batter). If the loaf is browning too quickly, tent with foil for the last 15 minutes.

Cool properly: Let the loaf cool in the pan for 15 minutes, then lift it out and cool on a rack for at least 1 hour. This helps the crumb set and prevents crumbling.

Slice and enjoy: Use a serrated knife for neat slices. Serve warm or at room temperature.