Preheat the oven to 425 degrees F.
Place the puff pastry rectangles onto a silpat lined baking sheet. Add the sugar, salt, lemon juice and vanilla bean seeds to the apples. Stir to combine. Allow to sit for a few minutes.
Arrange the apple slices on the pastry rectangles in a straight line, overlapping as you go. Dot the top with little bits of the butter. Bake until the pastry is puffed and golden brown, about 20 minutes.
Remove from the pan immediately and place on a serving platter. Serve with caramel sauce on the side.