Preheat & Prep.To start, preheat the oven temperature to 350 degrees F. Line a 9x5" bread pan with parchment paper (I like to have the parchment hang over the long sides like handles so I can easily lift the bread out when it's done cooking)
Brown the butter. In a light-colored saucepan, melt the butter over medium heat, stirring constantly. When the butter starts to bubble and foam, pay close attention and watch for it to brown. When the butter under the foam is golden and honey-colored and smells sweet, remove the pan from the heat and pour into a stand mixer or mixing bowl to cool slightly. (I'd recommend giving it 15-20 minutes to cool!)
Mix Wet Ingredients. Add brown sugar to the brown butter and stir until the mixture looks like wet sand. Mix in the mashed bananas, eggs and vanilla.
Add Dry Ingredients. Then add gluten-free flour, baking soda, and salt. Stir to combine until no lumps of flour remain. Fold in chocolate chips or nuts, if using.
Bake Banana Bread. Pour the batter into your prepared loaf pan and bake at 350 degrees F. for 60-70 minutes, or until the top is a deep golden color. To be extra sure the bread is done, an instant-read thermometer should register 200 degrees F. when inserted into the center of the loaf. If you find the top is browning too quickly, you can lightly cover the loaf pan with foil.
Cool. Allow the bread to cool 5 minutes in the loaf pan before transferring to a cooling rack. Allow the bread to cool at least 20 minutes before you slice it for best results.
Serve & Store. Enjoy cooled banana bread right away, or store in an airtight container at room temperature 2-4 days. Or, freeze up to 2 months.