Preheat oven to 425°F (220°C). Place a 10-inch cast-iron skillet in the oven to preheat.

In a blender, combine eggs, milk, flour, salt, and nutmeg. Blend until smooth.

Remove the hot skillet from the oven. Add 3 tablespoons of butter to the skillet.

Return the skillet to the oven until the butter is melted and bubbling.

Pour the batter into the hot skillet.

Bake uncovered for 20 minutes, or until the pancake is puffed and the edges are browned and crisp.

While the pancake is baking, prepare the apple topping.

In a separate skillet, combine sliced apples, 3-4 tablespoons of butter, and sugar.

Cook over medium heat, stirring occasionally, until the apples are tender and caramelized.

Once the pancake is baked, remove it from the oven.

Spoon the caramelized apple topping onto the baked pancake.

Sprinkle generously with confectioners' sugar.

Cut the pancake into wedges and serve immediately.