1 tablespoonapricot jelly or jam, optional for glaze
Make the crust: Line a baking sheet with parchment paper. In a food processor fitted with the steel blade, combine the flour, salt and sugar. Pulse briefly to combine. Add the cold butter and process just until the butter is the size of peas, about 5 seconds. Sprinkle the ice water over the mixture and process just until moistened and very crumbly, about 5 seconds. Transfer the dough to a lightly floured work surface and knead a few times, just until it comes together into a cohesive ball. Pat the dough into a disk. Flour your work surface again and dust the dough with flour, as well. Using a rolling pin, roll into a circle 8 to 10 inches in diameter, turning and adding more flour as necessary so the dough doesn’t stick. Transfer the dough to the parchment-lined baking sheet and refrigerate while you prepare the filling (you’ll roll the dough out further on the parchment paper so go ahead and clean your work surface).
Make the Filling: Peel, core, and cut the apples into 1/8-inch-thick slices (you should have about 4 cups) and place in a large bowl. Add the sugar, vanilla, cinnamon, melted butter, and salt; toss to combine.
Take the dough from the fridge and slide the parchment paper onto the countertop. Roll the dough, directly on the parchment paper, into a 14-inch circle about 1/8 inch thick. It’s fine if the edges are a little ragged. Place the parchment and dough back on the baking sheet – the pastry should curve up the lip of the pan.
Assemble the tart: Sprinkle the flour evenly over the pastry. Arrange the apple slices on top in overlapping concentric circles to within 3 inches of the edge. Don’t worry about making it look perfect! It doesn’t make much difference in the end and you don’t want the dough to get too warm. Fold the edges of the dough over the apples in a free-form fashion, working your way around and creating pleats as you go. Patch up any tears by pinching a bit of dough from the edge.
Using a pastry brush, brush the pleated dough evenly with the beaten egg. Sprinkle 1 tablespoon of the turbinado sugar over the top crust and 1 tablespoon over the fruit. Chill the assembled tart in the fridge for 15 to 20 minutes.
Meanwhile, preheat the oven to 350°F and set an oven rack in the center position.
Bake for 55 to 65 minutes, or until the apples are tender and the crust is golden and cooked through. (It’s okay if some of the juices leak from the tart onto the pan. The juices will burn on the pan but the tart should be fine -- just scrape any burnt bits away from the tart once it’s baked.) Transfer the pan to a rack and let cool.
While the tart cools, make the optional glaze. In a small bowl, mix the apricot jam with 1-1/2 teaspoons water. Heat in the microwave until bubbling, about 20 seconds. Using a pastry brush, brush the apples with the apricot syrup.
Use two large spatulas to transfer the tart to a serving plate or cutting board. Slice and serve warm or at room temperature. The tart is best served on the day it is made, but leftovers will keep, loosely covered on the countertop, for a few days.
Make Ahead: The dough can be made up to 3 days in advance and refrigerated. Allow it to sit at room temperature for about 15 minutes or until pliable before rolling.
Freezer-Friendly Instructions: The assembled tart may be frozen for up to 3 months. To freeze, place the baking sheet in the freezer until the tart is frozen, then wrap tightly. (Wait until right before baking the tart to brush the beaten egg and sprinkle the sugar onto the crust.) Bake directly from the freezer. (It may take a few extra minutes to bake from frozen.)