4 large firm apples, preferably Granny Smith
1 cup (7 ounces) plus 2 tablespoons (3⁄4 ounce) granulated sugar
Juice of 1⁄2 lemon
Pinch of kosher salt
6 tablespoons (3 ounces) unsalted butter
All-purpose flour, for dusting
About 14 ounces prepared puff pastry (thawed, if frozen)
Preheat the oven to 375°F; position the rack in the middle of the oven.
Peel and core the apples and cut them into 1⁄2-inch-thick wedges. Place the apples in a large bowl, add 2 tablespoons of the sugar, the lemon juice, and salt, and toss to combine.
In a 9-inch ovenproof skillet (not nonstick), heat the remaining 1 cup sugar over medium heat. Cook, stirring with a silicone spatula, until the sugar has melted. As the sugar melts, it will start to caramelize and turn golden. Once the sugar has melted into caramel, cook the caramel, swirling it gently from time to time, until it is the color of a copper penny, 5 to 7 minutes. Turn o the heat and add 4 table- spoons of the butter to the caramel, stirring with a spatula to let it melt into the sugar. This will stop the cooking process. Add the apples along with any juices that have collected at the bottom of the bowl, and toss with the caramel a few times until well coated. Cut the remaining 2 tablespoons butter into small pieces and place on top of the apples.