Preheat your oven to 375°F and lightly grease a small oven-safe baking dish with a touch of butter.
In a medium mixing bowl, whisk together the gluten-free oats, vanilla protein powder, baking powder, sea salt, and half of the ground cinnamon.
Add the whole milk, vanilla extract, and half of the Greek yogurt to the dry ingredients, stirring until the batter is well combined.
Pour the oat mixture into the prepared baking dish and bake for 22 to 25 minutes until the top is firm and slightly golden.
While the oats are baking, core and dice the apples into small, even cubes.
Melt the butter in a small skillet over medium heat, then add the diced apples, maple syrup, and the remaining ground cinnamon.
Sauté the apples for about 8 minutes, stirring occasionally, until they are soft, fragrant, and coated in a light syrup.
Remove the baked oats from the oven, top with the warm stewed apples, and finish with the remaining dollop of Greek yogurt.