To prepare the dough, put the flour and salt in a food processor with the dough blade and pulse together briefly.
Meanwhile, fill a glass measuring cup with ½ cup water and add a few ice cubes to it.
Take the cold butter straight out of the fridge and cut it into tablespoon sized chunks. Sprinkle the pieces of butter on top of the flour in the food processor. Be careful to spread out the butter as opposed to letting it all clump together in one place.
Turn on the food processor and blend until the mixture resembles a crumbly meal. While the food processor is still running, add ⅓ cup water through the top. Watch the dough come together and add 2 – 3 more teaspoons of water as needed so a dough ball will form. If some of the dough is in a ball and some is stuck to the sides, that is okay. You can fix it with your hands. At this point, the dough could be stored in the fridge in plastic wrap for up to 3 days or in the freezer (in a freezer safe container) for up to 6 months.
Remove the dough from the food processor, break it into two equal-sized pieces, and put the first one on a lightly floured counter or large cutting board. With a rolling pin (and another sprinkling of flour), flatten out the dough to one big rectangle the size of your quarter sheet pan (9 x 13 inches). Trim any uneven ends and use those to patch other edges as necessary. Transfer to the bottom of the pan.
Roll out the second piece of dough to the same size and set aside.
To prepare the filling, core and slice the apples into 8 slices each (I use a corer/slicer tool to make this job quick and easy). Then thinly slice each piece into thirds. Toss the pieces in a large bowl with the honey, lemon juice, cinnamon, and nutmeg.
Pour the mixture into one even layer on top of the crust. Slice thin pats of butter out of the one tablespoon (if using) and spread them over the top. Place remaining crust on top, pinch the edges together and make some vent holes with a fork.
Place on the lowest rack in the oven and bake for 15 minutes. Lower the heat to 350 and bake for 40 to 45 minutes more until the crust begins to turn golden brown and the filling is bubbly. Serve warm with homemade vanilla ice cream, if desired. Enjoy!