Heat the oven to 350F and oil one 10 ounce ramekin.
Mash the banana thoroughly in the ramekin itself, then whisk in the egg and almond milk. Lumps of banana stay lumpy through baking.
Stir in the oats, cinnamon and baking powder, then fold in the protein powder last with as few strokes as possible.
Let the mixture stand 5 minutes before baking. The oats hydrate and the powder disperses, and this rest is what prevents a dry, dense result.
Bake 22 to 25 minutes, until the top is set and springs back lightly when pressed. A skewer should come out with a few moist crumbs, not clean; baked until fully dry it turns rubbery.
Cool 5 minutes before eating, warm, straight from the ramekin.