Preheat oven to 450°.
Heat a 10" cast iron skillet over medium heat.
Melt 2 Tablespoons of butter.
Combine apple slices and granulated sugar in a bowl.
Add to melted butter and sauté 3-5 minutes or until the apples are tender.
Remove apples from skillet.
Whisk together eggs and milk in a medium bowl. Whisk in flour, cinnamon, salt, and nutmeg.
Melt remaining 2 Tablespoons of butter in skillet over medium heat.
Pour egg mixture over butter and add apples.
Bake at 450° for 15-20 minutes or until golden brown and pancake is puffed.
Remove from oven, let cool for 5 minutes and sprinkle with powdered sugar.