Place 6 tablespoons butter in a 10-inch ovenproof skillet (preferably cast iron) in a 400 degree F oven until butter melts. In a medium bowl, beat eggs until combined. Add flour, milk, 1/4 teaspoon nutmeg, and the salt; beat until smooth. Immediately pour batter into the hot skillet. Bake for 20 to 25 minutes or until puffed and well browned.