Grease and flour a large loaf pan using vegetable oil and Gluten-free flour.
In a mixing bowl, combine the gluten-free flour blend, coconut flour, cinnamon, baking powder, baking soda and the salt. Set aside.
In a large mixing bowl, whisk together the oil and sugar. Add in the eggs and vanilla and whisk until well combined.
In a small bowl, mash the banana until no large lumps remain. Stir in the milk.
Add half of the flour to the oil/egg mixture and stir in. Add half of the banana mixture and mix in. Stir in the remaining flour mixture and then add in the remaining banana mixture, stirring until just combined.
Scrape the batter into the prepared loaf pan and bake in the preheated oven for 50-60 minutes. A toothpick inserted into the center should come out clean.