Start the caramel sauce first, because it needs to cool: in a 10 inch cast iron pan, melt the butter and then whisk in the brown sugar until it’s melted. Let simmer a few minutes without stirring, until it bubbles. Set aside to cool.
Put into a food processor bowl the flour, sugar and salt, and pulse to combine. Add in the cold butter and pulse until crumbly. With the processor running add in the vinegar and ice water. I found I needed to add a bit more water than called for. Can also be done by hand with a pastry knife.
Turn out onto a floured surface and knead once or twice, and divide into two pieces. Form into a disc, and wrap in plastic wrap. Put in the refrigerator to chill. Chilling will re-harden the butter than may have softened while making the dough. Cold butter heated up in the hot oven will turn into a flaky crust – and this much butter makes it flay for sure!
Here’s where I peeled and sliced the apples.
Roll out one of the pie crust disc’s into a large enough circle to fit into the skillet. Put it right on top of the caramel mix. Yep, that’s what you do.It's also why the caramel needs to cool, so as to not melt the pie crust dough.
If you like, beat up an egg and 1 tbsp water and brush the crust, then sprinkle with the sugar. Or just plain sugar sprinkled on top, a la Grandma style.
Enjoy warm, plain or with ice cream, and any left overs can be heated by the slice for a few minutes to re-warm if desired.
The caramel sauce that is under the crust soaks into it and into the apples – and the crust gets nice a crispy from the heat of the cast iron. Delicious.