In the bowl of a food processor, pulse together the flour, salt, and sugar until combined. Pulse in the cold butter until the mixture resembles coarse crumbs, then pulse in the ice water just until the dough begins to gather. Transfer to a lightly floured counter, knead a few times until smooth, then press into a 1/2-inch-thick disc. Wrap tightly in plastic wrap and refrigerate 1 to 2 hours.

Preheat the oven to 400°F. Line a baking sheet with parchment paper. In a large bowl, toss the sliced peaches with the brown sugar, cornstarch, cinnamon, ground ginger, salt, vanilla, and lemon zest and juice. Let the mixture sit for 20 minutes, stirring occasionally.

On a lightly floured surface, roll the chilled dough out to a roughly 14-inch circle. Spoon the peach filling onto the dough, leaving about 1 inch of dough uncovered around the edge. Fold the edges of the dough up and over the filling to encircle it. Drizzle any remaining juice from the bowl over the peaches. Transfer the baking sheet to the refrigerator to chill for 10 minutes.

Brush the folded dough edges with egg wash and sprinkle liberally with turbinado sugar. Bake 45 to 50 minutes, rotating the pan halfway through, until the filling is bubbly and the crust is deep golden brown and baked through.

Serve warm or at room temperature.