Preheat the oven to 350°F and lightly grease a small 6x3-inch mini loaf pan.
In a medium mixing bowl, mash the half banana with a fork until it reaches a smooth consistency.
Add the Greek yogurt, whole egg, egg whites, and vanilla extract to the bowl, whisking until the mixture is uniform.
Fold in the oat flour, hemp hearts, flaxseed meal, baking powder, cinnamon, and sea salt, stirring until no dry clumps remain.
Transfer the batter into the prepared mini loaf pan and use a spatula to level the top.
Bake for 28 to 32 minutes, or until the top is golden brown and a toothpick comes out clean from the center.
Allow the loaf to cool in the pan for at least 10 minutes to set before slicing into thick, satisfying pieces.