Preheat oven to 400°F. Line a baking sheet with parchment paper or a silicone baking mat. Set aside.

Core the apple and cut it into ⅛-inch thick slices. Using a mandoline is the fastest way to get thin, even slices.

Add the apple slices to a bowl along with the lemon juice, sugar, apple pie spice, and salt. Gently toss to coat the apples. Set aside.

Unfold the thawed puff pastry onto a clean work surface. Use a rolling pin to close up the seams and square up the pastry – you should end up with a 9x9-inch square.

Transfer the puff pastry to the prepared baking sheet. Using a sharp paring knife, score the pastry ½ inch from the edge all the way around, making sure not to cut all the way through the pastry. Use a fork to poke holes inside of the score lines.

Spread the apricot and vanilla mixture over the pastry, making sure to keep it inside of the score marks. Arrange the apple slices in rows on top of the pastry, slightly overlapping the slices. You may not use all of the slices – that’s ok.

Bake the tart for 30-35 minutes, until the edges are puffed and golden, the apples are soft, and the underside of the tart is golden.

Let the tart cool for at least 10-15 minutes before serving. To serve, dust with powdered sugar, top with a drizzle of salted caramel sauce, and/or serve with a scoop of vanilla ice cream.