Thaw puff pastry sheet on the counter top or overnight in the refrigerator.
Preheat oven to 400 degrees F. Line a baking sheet with parchment paper.
Roll puff pastry on a lightly floured surface to a 10x12-inch rectangle. Then, cut in half (two 6x10-inch rectangles).
Peel apples and cut them in half through the stem. Remove the core. Slice thinly using a knife or mandolin slicer.
Heat Sea Salt Caramel Sauce in small saucepan or microwave until it is pourable, but not hot.
Place apple slices in two rows on top of each pastry so that they overlap and leave a 1/2-inch border clear. Gently brush Sea Salt Caramel Sauce over the apples.
Combine sugar and cinnamon and sprinkle over tarts. Dot with butter.
Bake 20-24 minutes or until the pastry is golden brown and puffed and the apples are tender.
Drizzle with additional Sea Salt Caramel Sauce and cut into squares. Serve with sweetened whipped cream or vanilla ice cream.