Prepare the fruits by washing and slicing the peaches, removing the pits, and placing them in a mixing bowl. Drizzle with lemon juice and sprinkle with granulated sugar. Fold in raspberries if using, and let sit for one hour.

After macerating, drain excess liquid and combine the fruit with brown sugar and corn starch in the same bowl, stirring until evenly coated.

Preheat oven to 350°F (180°C). Roll out the pie crust and line a 9-inch pie pan. Brush the bottom with egg wash, fill it with the fruit mixture, and top with lattice strips or a solid crust with slits.

Refrigerate the assembled pie for 30 minutes to relax the crust.

Bake in the preheated oven for 35 to 40 minutes until the crust is golden and the filling bubbles through the slits.

Allow the pie to cool on a wire rack for 2 to 3 hours before serving.