Slice 4 ripe bananas lengthwise. Add them to a baking tray, and spray them lightly with coconut oil.
Broil bananas in the Sharp Superheated Steam Countertop Oven for 10 minutes, until the tops of the bananas have begun to brown.
Line a 9x5 loaf pan with parchment or baking paper, and set aside.
Mix together optional streusel topping ingredients. See notes below for variations on streusel topping for the Blueberry Pecan and Raspberry Chocolate Chip variations.
If using a conventional oven, preheat oven to broil, and broil bananas for 15 minutes, or until tops have begun to brown.
In a mixing bowl, add oat flour, almond flour, flax meal, baking powder, salt, and cinnamon. Mix to combine.
In a smaller bowl, add yogurt, eggs, and coconut oil (melted). Mix well to combine, and then pour into the bowl with dry ingredients. Stir until just combined.
Add caramelized bananas to batter, along with walnuts, or optional additions (blueberries, raspberries or chocolate chips). If adding chocolate chips, allow the bananas to cool before mixing in to the batter, otherwise the chocolate will melt. Fold additional ingredients into batter.
Pour the batter into prepared loaf pan, and top with the optional streusel topping.
Bake in the Sharp Superheated Steam Countertop Oven at 350º F for 32 minutes.
If baking in a conventional oven, preheat oven to 350º F and bake for 45-52 minutes, or until the center is set and the top is golden brown.