For the pie dough:
2 cups all-purpose flour
½ teaspoon kosher salt
1 tablespoon sugar
12 tablespoons (1½ sticks) cold unsalted butter, cut into pieces
½ cup ice water, plus more if needed
For the filling:
4 apples, peeled, cored and sliced ¼-inch thick
Finely grated zest of 1 lemon
1 tablespoon fresh lemon juice
¼ cups sugar
½ teaspoon ground cinnamon
Kosher salt
Caramel sauce, made with ½ teaspoon salt, for serving
Combine the flour, salt and sugar in the bowl of a food processor. Sprinkle the butter over the top and pulse for a few seconds, or just until the butter is broken up and the mixture looks coarse. Evenly sprinkle the water over the flour mixture, then pulse just until the dough starts to come together. Transfer to a sheet of plastic wrap and press into a disk. Refrigerate for at least 30 minutes and up to 1 day before using.
Line a baking sheet with parchment or a nonstick baking mat. Place the apples, lemon zest and juice, sugar, cinnamon and a pinch of salt in a large bowl. Toss together to combine.
Transfer the dough to a lightly floured work surface and divide into 6 equal pieces. Roll each piece into a round about ⅛-inch thick. Evenly space the dough rounds on the prepared baking sheet.
Divide the apples between the dough rounds, spreading into an even layer and leaving a 1-inch border of dough. Fold the edge up and over the apples, loosely pleating the dough and leaving the apples uncovered in the center. Refrigerate for about 30 minutes. Meanwhile, heat the oven to 400º.
Bake the galettes until the crust is golden brown and the apples are tender, about 40 minutes. Allow to cool on the baking sheet on a wire rack.
When ready to serve, drizzle the galettes with warm caramel sauce and serve immediately.