Preheat your oven to 350°F and lightly grease a standard donut pan with a small amount of coconut oil.
In a medium mixing bowl, whisk together the egg, Greek yogurt, and vanilla bean paste until the mixture is smooth and well combined.
Add the vanilla whey protein powder, oat flour, baking powder, and sea salt to the wet ingredients.
Fold the dry ingredients into the wet until a thick, uniform batter forms, being careful not to over-mix.
Transfer the batter to a piping bag or a plastic bag with the corner snipped off, and pipe the mixture evenly into the donut cavities.
Bake for 10 to 12 minutes, or until the donuts are springy to the touch and a toothpick comes out clean.
While the donuts cool, whisk together the maple syrup and melted coconut oil in a small shallow bowl to create the glaze.
Once completely cool, dip the top of each donut into the glaze and let them set on a wire rack before serving.