Whisk the flour, sugar and salt together then add to the egg mixture in three parts, mixing completely after each addition until the mixture is smooth.
Add the milk in slowly, beating continuosly to avoid lumps from forming.
Mix in the melted butter.
Place a 9 or 10 inch oven safe skillet on the stove and heat on low. Melt the remaining 2 tbsp of butter. When pan is warm, pour the batter into skillet.
Bake at 425 °F for 15-20 minutes until puffy and browned.
While this is baking, melt the butter in a small pan and add the apples, sugar and cinnamon. Cook slowly, stirring, over low heat until the apples are glazed and softened slightly.
Serve in the middle of the dutch baby OR on the side so each person can top their slice themselves.
Spoon onto center of baked pancake or serve on the side.