Core and thinly slice the apple into uniform wedges.
In a large mixing bowl, whisk together the Greek yogurt, liquid egg whites, whole egg, and vanilla extract until the mixture is completely smooth.
Gently fold in the oat flour, baking powder, and half of the cinnamon until just incorporated, being careful not to overmix.
Heat a large non-stick griddle or skillet over medium heat and lightly coat with half of the ghee.
Pour the batter onto the skillet to form three to four pancakes, cooking until small bubbles appear on the surface.
Flip the pancakes and cook for another 2 minutes until the edges are firm and the centers are golden brown.
While the pancakes finish, heat a separate small skillet with the remaining ghee over medium-high heat.
Add the apple slices, the remaining cinnamon, and the maple syrup to the small skillet, sautéing for 3-5 minutes until the apples are tender and glazed.
Stack the pancakes on a plate and spoon the warm caramelized apples and any remaining pan sauce over the top.