Preheat a 10-in. cast-iron skillet in a 425° oven. Meanwhile, in a blender, combine the eggs, milk, flour, salt and nutmeg; cover and process until smooth. , Add butter to hot skillet; return to oven until butter bubbles. Pour batter into skillet. Bake, uncovered, until pancake puffs and edges are browned and crisp, 20 minutes. , For topping, in a skillet, combine the apples, butter and sugar; cook and stir over medium heat until apples are tender. Spoon into baked pancake. Sprinkle with confectioners' sugar. Cut and serve immediately.