1. Wash the apples, peel them, and remove the core.
2. Cut the apples into half-centimeter-thick slices.
3. In a bowl, put the lemon juice and dip the apples for a couple of minutes.
4. Spread the puff pastry dough and prick it all over so that it does not puff up.
5. Distribute the apple slices over the puff pastry and drizzle with the butter (previously melted).
6. Sprinkle sugar all over the cake.
7. Place the puff pastry on a baking sheet (previously greased).
8. Bake for 30-40 minutes at 390ºF.
9. Remove and sprinkle with some confectioners' sugar.