In a large bowl, mash together the 5 whole bananas, eggs, oil sugar, cinnamon until well combined. Stir in the oat flour until the batter comes together without any flour lumps.
In a medium cast-iron skillet over low heat, whisk the coconut shortening and maple syrup until well combined. Increase the heat to medium and cook for 3 to 5 minutes, or until the mixture starts to thicken and bubble. Pour into and 8" x 8" baking dish.
Lay the 2 sliced bananas in a single layer on top of the maple caramel. Gently scoop the batter over the bananas and caramel, evenly distributing it and being careful not to move the bananas too much. Spread to even out.
Bake for 40 to 45 minutes, or until a toothpick comes out clean. Remove and let cool completely before flipping over onto a platter or cutting board.