Preheat the oven to 350ºF and grease a 9x5-inch loaf pan.
In a large bowl, whisk together the 3 large ripe bananas, 3 large eggs, and ¼ cup oil, then stir in the 1 ¾ cups gluten free flour, ¾ cup granulated sugar, 2 teaspoons baking powder, 1 teaspoon ground cinnamon, and 1 teaspoon ground cinnamon and ½ teaspoon fine sea salt, stirring until a smooth batter forms. Pour the batter into the prepared pan, smooth the top, then rest the batter until the oven is fully heated.
Bake the loaf for about 50-55 minutes, when a tester comes out clean or with a few moist crumbs.
Cool the bread in the pan for 20 minutes, then cool it on a rack. I like to cool the bread completely so that the crumb sets, but it's OK to cut into it after about 30 minutes (it's delicious warm!).
Notes
Make sure the bananas are really ripe. The ripest bananas have lots of brown spots, and they will be sweeter and more flavorful, which will create a super delicious baked loaf.
Puree or mash. Sometimes I will puree my bananas using a blender or food processor so that they are ultra smooth. Otherwise, I mash them well with a fork, which works fine, too.
Rest the batter. Don't turn the oven on until you have assembled the batter. While the oven is preheating, the oat flour will have time to hydrate (soak up the moisture in the batter), making for that gorgeously soft crumb.
Try other spices. Instead of cinnamon, use ground ginger or cardamom. Add a pinch of nutmeg for a slightly different flavor note. Or, add fresh peeled and grated ginger!
Add vanilla. Whisk in 2 teaspoons of pure vanilla extract or vanilla bean paste when combining the wet ingredients.
Make it refined sugar-free. Substitute coconut sugar or maple syrup for the sugar.
Cool completely. This is a moist loaf, so for the crumb to fully set, make sure to cool the bread for about 1 hour before slicing it.
Make it richer. If you love the buttery note that comes from using butter, feel free to substitute melted butter for the oil. For a dairy-free version, use dairy-free butter.