Preheat the oven to 375 degrees

Roll out the pastry with a floured rolling pin and cut into a 10″ circle, place it on a baking sheet in the refrigerator until you need it

Melt the butter in a 10″ cast iron skillet, add sugar, lemon juice, vanilla and a pinch of salt

Whisk the sauce over medium heat until it turns into caramel, about 5 minutes, lowering the heat if necessary

Remove the pan from the heat and place the apples on top of the caramel

Lay the sheet of puff pastry over the apples, tucking it in around the edges

Poke the pastry with a fork a few times to let the steam escape

Place the skillet in the oven and bake for 40 to 45 minutes, or until the pastry is golden brown

Let cool for at least 10 minutes and then carefully (it’s really, really hot), turn it out onto a serving plate.