Preheat the oven to 350°F (175°C). Lightly grease an 8-inch round cake pan and line the bottom with parchment paper.
In a large mixing bowl, combine the mashed bananas, maple syrup, melted coconut oil, and vanilla extract. Stir until smooth and well combined.
In a separate bowl, whisk together the almond flour, gluten-free oat flour, baking soda, baking powder, salt, and ground cinnamon.
Gradually add the dry ingredients to the wet ingredients, mixing gently until just combined. Do not overmix.
Pour the batter into the prepared cake pan, smoothing the top with a spatula.
Bake for 38 to 40 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cake from the oven and allow it to cool in the pan for 10 minutes.
Transfer the cake to a wire rack to cool completely before slicing and serving.