German Apple Skillet Cake

3 large eggs
3/4 cup all-purpose flour
2 tablespoons granulated sugar
3/4 cup milk
1 teaspoon cinnamon
1 teaspoon vanilla extract
2 cups thinly sliced tart green apples (about 2)
1/4 cup unsalted butter
Maple syrup

In a large bowl, whisk together the eggs, flour and sugar until the mixture is smooth. Whisk in the milk, cinnamon and vanilla extract, whisking until the mixture is combined well, then stir in the apples.

In a 9- or 10-inch cast iron skillet, melt the butter over moderate heat. Pour the batter into the skillet, spreading the apples evenly. Bake the cake in the middle of a 375 degree F oven for 30 minutes, or until it is puffed and begins to pull away from the sides of the skillet. Serve the cake cut into wedges with maple syrup.