For the dough: Put the flour and salt into the bowl of a food processor and whirl it up until the flour is fully aerated and fluffy.
Add the butter and cream cheese and pulse several times, until the butter and cream cheese are roughly broken down into pieces the size of lima beans. (They won't all be the same size.)
Add 4 tablespoons cold water to the flour mixture and pulse several times again. The flour should be starting to clump up with the butter and cream cheese, which will look more distinct in the mixture now. Pinch a bit of the flour and fats together in your fingers. If they stick together, the dough is ready. Most of the time, it might take a couple more tablespoons of water to make the dough cohere. (The mixture should look like cheese curds. Don't add so much water that the dough comes together in one clump.)
Dump the dough onto a piece of parchment paper, taking care to remove the blade of the food processor. Using the heel of your hand, press the curds of dough together to form a coherent pie dough. Fold the dough onto itself several times, like turning the pages of a book. This will make the final dough flakier. Shape the dough into one large ball, then cut it into 2 pieces and flatten each piece into a small disc. Wrap the discs of dough in plastic wrap and put them in the refrigerator for 30 minutes.
For the pie: Meanwhile, put the apples, sugar, flour, cinnamon, salt and nutmeg into a large bowl and toss them together. Let the filling sit while the pie dough is chilling.
Pull one of the discs of dough out of the refrigerator and put it on a piece of parchment paper. Gently flatten it just a touch. Put another piece of parchment paper on top and roll out the dough, moving the rolling pin in small increments, like moving around the face of a clock. When the dough is large enough to be just bigger than a 9-inch pie pan, peel off the top piece of parchment paper and flip the dough onto a pie pan. Peel off the parchment paper. If any pieces stick to the paper, don't worry; simply peel them off and pat them in place.
Tumble the apple filling into the pie shell. Roll out the remaining disc of dough the same way and put it on top of the pie. Tuck the edges together and crimp them. Make 3 slits in the top of the pie for steam vents. Put the pie into the freezer, 15 minutes.
Meanwhile, preheat the oven to 425 degrees F. Line a baking sheet with parchment paper.
Put the pie onto the prepared baking sheet and bake 15 minutes, then drop the temperature to 375 degrees F and bake until the crust is warm and browned and the juices from the apples are oozing out of the pie, 45 minutes to 1 hour.
Allow the pie to cool to room temperature before slicing into it, about 1 hour.