Heat oven to 400 Deg. F. Use a baking steel or pizza stone if you have one and preheat the oven with the steel or stone on the middle rack. If not, set out a large baking sheet instead.
Place a rectangular piece of parchment paper on your counter to thaw one piece of puff pastry at a time.
While the puff pastry is thawing, prep your apples.
Peel and core the apples and slice thinly. Place in a large bowl, cover the apples with cold water and add in the lemon juice and salt. Gently stir and set aside.
When the puff is thawed to very cool room temperature, gently roll out to about 9 x 12 inches
After rolling score along the edges with a knife, being careful not to cut all the way through. Then pierce the middle all over with a fork, again being careful not to cut all the way through.
Place the prepped puff pastry back in the refrigerator for 5 minutes to firm back up.
Working quickly, spread half a cup of the apple butter on the pastry inside the edge score lines. Remove apple slices from water and gently pat dry with paper towels, arrange the apples on top of the pastry in any way you like. Drizzle with a tablespoon of melted butter then sprinkle the apples with half the cinnamon sugar.
Place the tart with the parchment paper on a baking sheet or directly onto the baking steel/stone. Bake for 20-25 minutes until golden, crisp and puffed up.
If using a baking steel or stone, remove the parchment paper halfway through to get a super crispy bottom.
Once baked, remove from the oven and transfer to a cutting board to cool slightly. Drizzle with caramel sauce and dust with half of the powdered sugar.
You can prep the second pastry while the first one is baking. Bake that one as soon as the first one is out of the oven. If you have a large enough baking stone or baking sheet you can bake two tarts at once.