Preheat the oven to 190°C (375°F). Lightly score a sheet of All-Butter Puff Pastry to allow steam to escape and keep it chilled until ready.
Peel, core and halve or quarter the Apple depending on size so the pieces are uniform (about 6–8 medium apples total for a 9–10 inch pan).
In a heavy, ovenproof 9–10 inch skillet or tarte tatin pan, sprinkle an even layer of Granulated Sugar over the bottom and warm it over medium heat. Let the sugar melt and turn a deep amber, swirling the pan occasionally—avoid stirring vigorously to prevent crystallization.
When the sugar is a rich caramel color, add the Unsalted Butter in pieces and a small pinch of Salt and stir carefully until the caramel is smooth.
Remove the pan briefly from the heat and arrange the prepared Apple pieces tightly in the caramel, rounded side down, packing them snugly as they will shrink while cooking.
Return the pan to medium heat and cook the apples in the caramel for 8–10 minutes until they begin to soften and the caramel is bubbling around them.
Drape the chilled All-Butter Puff Pastry over the apples, tucking the edges down around the fruit inside the rim of the pan. Trim any excess pastry and make a few small slits to vent.
Bake in the preheated oven for 25–30 minutes, or until the pastry is golden brown and the caramel is actively bubbling.
Let the tart rest for 5 minutes out of the oven (not longer than 10 so the caramel doesn't set too hard), then carefully invert onto a large serving plate—use oven mitts and a plate slightly larger than the pan, holding them together tightly and flipping in one confident motion.
Serve warm or at room temperature, optionally with crème fraîche or vanilla ice cream.
