Prep your 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.
Mash the bananas: In a large bowl, mash the bananas until mostly smooth.
A few small lumps are fine.
Whisk the wet ingredients: Add the eggs, oil, brown sugar, and vanilla. Whisk until the mixture looks glossy and well combined.
Combine dry ingredients: In a separate bowl, whisk the gluten-free flour, baking soda, baking powder, salt, cinnamon, and nutmeg. This helps prevent clumps and ensures even rise.
Bring the batter together: Add the dry ingredients to the banana mixture.
Stir with a spatula until just combined. Do not overmix. Fold in nuts or chocolate chips, if using.
Fill the pan: Scrape the batter into the prepared loaf pan and smooth the top. If you like, sprinkle a little sugar on top for a slight crackly crust.
Bake: Bake for 55–65 minutes, or until the top is deeply golden and a toothpick inserted in the center comes out clean or with a few moist crumbs.
If the top browns too quickly, tent loosely with foil.
Cool properly: Let the bread cool in the pan for 10–15 minutes. Lift it out using the parchment, then cool completely on a rack before slicing. This step helps the loaf set and prevents crumbling.
Slice and serve: Use a serrated knife for neat slices. Enjoy warm, at room temperature, or toasted with butter or nut butter.