1. Slice off bottom of each apple creating a flat base. Peel and quarter apples, removing core and seeds. In a large bowl, toss sliced apples with lemon. Transfer to refrigerator and let dry out overnight.
2. Heat oven to 375°. Spread butter on bottom of a 10-inch cast iron skillet, creating a thick, even coating. Sprinkle sugar evenly on top. Cut one apple slice into a thick disk to use as the center. Arrange remaining apple slices, each one standing on its flat end, in circles around the center piece. The design should look like a flower.
3. On a floured worked surface, roll out puff pastry to ⅛-inch thick. Use an upside down bowl or plate as a guide to cut out a circle of pastry about the same size as the skillet. Place pastry gently over apples and tuck around.
4. Place skillet on stovetop over medium heat. Cook until juices boil around the edges and turn a deep golden-brown, about 25 minutes. (If juices start to overflow while cooking, carefully spoon out excess and discard.) Carefully transfer skillet to oven and bake until pastry is browned, about 45 minutes.
5. Let cool 5 minutes then carefully invert onto a 12-inch serving platter. Serve warm or room temperature.