Preheat oven to 350 degrees F and line a loaf tin with nonstick parchment paper, allowing an inch or two to overhang the sides. Add oats to a high powered blender or food processor and blend until they form oat flour. You want it to be as fine a consistency as possible. Set aside 1/4 cup oat flour. Add remaining oat flour to a large mixing bowl, along with coconut flour, sea salt, 3 teaspoons cinnamon (1 tablespoon), baking powder and baking soda. Whisk to combine.

In the same blender or food processor (no need to clean!), combine banana, egg, 4 tbsp /1/4 cup softened butter or coconut oil, apple cider vinegar, vanilla and 4 tbsp/1/4 cup coconut sugar, then puree until smooth. If you don’t have a blender or FP, mash bananas with a fork until pulpy, then stir in remaining wet ingredients.

Add wet ingredients to dry and fold together to incorporate. Don’t over-mix, or the oat flour will bake into a gummy texture. In a small bowl, stir together the 1/4 cup oat flour you set aside, the remaining 2 tbsp coconut oil/butter, remaining 1/4 cup coconut sugar and remaining teaspoon cinnamon. This should be a crumbly consistency.

Add 1/2 of your batter to the loaf pan and spread in an even layer. Sprinkle crumble mixture down the center of the batter and press gently into the batter. Top with remaining batter; you can use a dampened spatula to smooth it without sticking. Bake for 35-40 minutes, or until the edges are golden brown and a toothpick comes out clean. Allow to cool at least 30 minutes before topping with melted coconut butter “icing” and slicing.