Step 1

Preheat oven to 400 degrees. In a 10-inch cast-iron skillet, melt butter and 3 tablespoons sugar. Add apple slices, and cook for 5 minutes, stirring occasionally.

Step 2

In a medium bowl, whisk together eggs, flour, milk, cinnamon, salt, and remaining tablespoon sugar. Pour batter slowly over cooked apple mixture. Transfer skillet to oven. Bake until dark golden brown, set in the center, and puffed around the edges, about 15 minutes. Dust with confectioners' sugar; serve immediately.