Remove your puff pastry from the freezer and let defrost on the counter while you caramelize the apples.
Build a fire in your oven and bring the temperature to 400 degrees. Alternatively, you could heat up either a gas, charcoal grill or regular oven. Just make sure you get the temp up to 400.
Melt the butter in a nine inch cast iron skillet over medium high heat. Once the butter has melted and is frothy, sprinkle the sugar evenly over the butter.
Lay the apples into the sugar in an overlapping pattern. This does not need to be perfect!
Sprinkle the cinnamon on the apples. Now - do not touch the apples. Let them cook undisturbed for about 10-15 minutes. You will know when it's ready because the caramel will be a golden/dark color bubbling up around the sides. When this happens, immediately remove from the heat.
Lay the puff pastry circle over the apples and transfer to the wood oven. Cook for 5 minutes until puff pastry has puffed and is golden brown.
Let the tart cool for about 12 minutes in the skillet then say a prayer and invert onto a plate. You can always rearrange the apple slices if some have stuck. ;)
Serve warm with vanilla ice cream!
You can make this in a regular grill or even an oven. To bake in an oven, preheat to 400 degrees and bake for 20 minutes until golden brown.