Preheat your oven to 190°C (375°F).
Peel, core, and slice the apples into quarters.
In a cast-iron skillet, melt the butter over medium heat.
Add the sugar and cook until it begins to caramelize, stirring occasionally.
Arrange the apple quarters in a circular pattern in the skillet.
Cook the apples for about 10 minutes until they begin to soften.
Sprinkle with a pinch of salt and, if desired, cinnamon or vanilla.
Roll out the puff pastry and place it over the apples, tucking the edges in.
Bake in the oven for 30-35 minutes until the pastry is golden brown.
Allow to cool for a few minutes before inverting onto a serving plate.