Preheat the oven to 350F. Line a small loaf pan (about 8×4-inches) with parchment paper.
In a large bowl, mash the bananas with a fork. Add the eggs, maple syrup and vanilla, whisking to combine. Add the almond flour, oat flour, flax, sea salt, baking soda and cinnamon. Whisk until no lumps remain.
Transfer to the loaf pan and top with the remaining banana.
Bake for 50 – 55 minutes, or until a toothpick comes out clean. Let cool in the pan.