Preheat the oven to 425°F. Position a rack in the lower third of the oven. Place a rimmed baking sheet on the rack while the oven heats.
In a large bowl, gently toss the peaches, raspberries, granulated sugar, brown sugar, cornstarch, lemon juice, vanilla extract, cinnamon, and salt until evenly combined. Let stand for 10 minutes.
4 cups cubed or sliced ripe peaches, 2 cups fresh raspberries, 3/4 cup granulated sugar, 1/4 cup light brown sugar, packed, 1/4 cup cornstarch, 1 tablespoon fresh lemon juice, 1 teaspoon vanilla extract, 1/2 teaspoon ground cinnamon, 1/4 teaspoon fine sea salt
On a lightly floured surface, roll one portion of the pie dough into a 12-inch circle. Transfer to a 9-inch pie plate, leaving any excess dough hanging over the edges.
Double recipe homemade pie crust
Spoon the filling into the prepared pie shell and scatter the butter over the top.
1 tablespoon unsalted butter
Roll the remaining pie dough into a 12-inch circle. Place it over the filling. Trim the excess dough, leaving about 1 inch overhang. Fold the dough under itself and crimp the edges to seal.
Using a sharp knife, cut several (3-6) vents in the top crust to allow steam to escape during baking. (Cut longer vents if using 3-4.)
Whisk together the egg and water. Brush the top crust evenly with the egg wash and sprinkle with coarse sugar.
1 large egg, 1 tablespoon water, Coarse sugar
Place the pie on the preheated baking sheet and bake for 20 minutes. Reduce the oven temperature to 375°F and continue baking for 35-45 minutes, or until the crust is deeply golden and the filling is bubbling through the vents. If the edges brown too quickly, loosely cover them with foil.
Transfer the pie to a wire rack and cool completely, about 4 hours, before slicing and serving.
Notes
If you have a lot of collected juices after macerating the fruit, you can scoop the fruit with a slotted spoon, then simmer the juices in a saucepan until reduced and syrupy, and pour over the fruit in the crust.