Step 1

Preheat the oven to 350 degrees F (175 degrees C).

Step 2

In a medium bowl, whip egg whites with an electric mixer until foamy. Sprinkle in 3 tablespoons of sugar while continuing to whip until stiff peaks form. In a separate bowl, stir together the flour, baking powder, and salt. Mix in the milk, egg yolks, and lemon juice until well blended, then fold in the egg whites using a rubber spatula or wooden spoon.

Step 3

Melt the butter in a large cast-iron (or other oven proof) skillet over medium heat. Spread the batter evenly in the pan. Layer the thinly sliced apple over the batter, and sprinkle with cinnamon and remaining sugar.

Step 4

Place the skillet in the oven, and bake for 10 minutes, or until the apples are golden brown and glazed looking. Cut into wedges to serve.