1 sheet frozen puff pastry (about 8-10 ounces) or you can use pie dough
3-4 lbs (about 8) medium sized firm apples such as Granny Smith, Fuji or Gala
1 stick of unsalted butter
3/4 cup sugar
Preheat oven to 400 degrees.
On a lightly floured surface, roll out puff pastry to 1/8-inch thickness. Using a knife, cut dough into a large circle that is 1 inch larger in diameter than the skillet you are using. Poke holes in dough with a fork, transfer to a parchment lined baking sheet and refrigerate until needed.
Peel, core and quarter the apples. (Don’t worry about apples browning since they will caramelize during baking.)
In a 9 or 10 inch cast iron skillet (or a non-stick skillet), over medium heat, melt butter. Remove from heat and stir in sugar until blended.
Arrange apples, rounded sides down, first making a tight circle around the inside edge of the pan. Pack the apples snug in the pan as they will shrink during baking. Make another circle of apples inside the first circle ,and then fill in the center of the pan with remaining apples. Cut smaller pieces of apple if needed to fill in any gaps.
Put the skillet over medium heat and cook until the sugar turns golden brown- about 15-20 minutes. Sugar will bubble. Do not stir and DO NOT TOUCH as sugar is very hot. Remove from heat and transfer the skillet to a baking sheet lined with parchment paper (for spillage.) Check skillet for any apple slice gaps. If there are any, move fruit into the right place with a spoon.
Center the crust on top of the apples and loosely tuck edges under slightly along edge of pan. Be careful not to burn your fingers. Use a knife if needed.
Bake for about 30 minutes until the top of crust is golden brown.
Cool on a baking rack for 2 minutes. Run a sharp knife along the inside edge of the pan. Using potholders or oven mitts, place a serving plate (slightly larger than the skillet) on top of the skillet and quickly flip over the whole tart onto your serving platter. If any pieces of apple stick to the pan, carefully place them back where they should be on the tart.
Let cool for 10 minutes. Tarte Tatin is best served right away and hot, with a scoop of vanilla ice cream on top. But it will also keep for a day at room temperature. Re-heat if you’d like.