Mix The Dry Ingredients. In a medium bowl, combine gluten-free flour, baking soda, cinnamon, and salt. Whisk until evenly blended, then set this mixture aside.
Mix The Wet Ingredients. In a large bowl, combine mashed bananas, melted butter, maple syrup, eggs, vanilla, and maple extract. Whisk until evenly blended.
Finish The Muffin Batter. Add the dry ingredients to the wet ingredients, and stir until just evenly blended, with no dry clumps of flour remaining.
If You Can, Let The Batter Rest! If time allows, let the batter rest at least 45-60 minutes, so the muffins rise taller in the oven and have a more tender crumb. If you're in a rush, you can skip this step, but the muffins won't rise as tall or be *quite* as tender.
Preheat & Prep. While the batter rests, preheat the oven to 375 degrees F. Line a 12-cup metal muffin pan with parchment paper liners.
Bake. Use an ice cream scoop or large cookie scoop to divide the batter into the prepared muffin tin. (You should have enough for 12 muffins!) Bake in preheated oven 17-20 minutes, or until the tops are golden brown and toothpick inserted in the center of a muffin comes out clean with just a few moist crumbs.
Serve & Store. Let the muffins cool on a wire rack 10-15 minutes before eating. Store leftover muffins in an airtight container 2-3 days at room temperature, or freeze up to 4 months.