Core the apples, then slice them into thin slices, less than ¼-inch thick. Place them into a bowl and mix in the lemon, cinnamon and brown sugar.
Thaw, then roll out the pastry into a large square or rectangle.
Preheat the grill to 425°F. Make sure that the Pizza Stone is on the grill preheating with the grill.
Lay a piece of parchment paper onto a baking sheet, then place the pastry on the parchment. Score a boarder about ½ to ¾-inch from the edges of the pastry, then lay the apple slices into a pattern that you like.
When you have finished layering the apple slices, slide the parchment and pastry onto the pizza stone and bake over indirect heat for about 20 minutes, or until the pastry is golden and puffed.
Remove the apple tart from the grill using the parchment paper to slide it back onto the baking sheet. Serve with caramel sauce, and maybe some vanilla ice cream or whipped cream.
Homemade Caramel Sauce
Pour the sugar into a pot and place it over medium low heat. Stir continuously with a soft spatula, or wooden spoon until it melts. It will begin by kind-of forming into stuck together shards, and eventually liquify. Once it liquifies things will start moving fast. Have the cream and butter ready.
Let the sugar cook in it's liquid state until it turns a lovely light tan color. Any darker, like a nice dark caramel and it will be burnt tasting. (learned the hard way)
As soon as you get the light tan color, remove the sugar from the heat and add the vanilla and stir in the butter one cube at a time, stirring until it's all mixed in. Then add the cream. Your caramel will freak out, like go all crazy and bubble and stuff. Stir until it is smooth. Then pour into a glass container to cool.