Preheat your oven to 425°F.
In a large mixing bowl, combine the sliced peaches, sugar, flour, lemon juice, cinnamon, and salt. Toss gently until the peaches are well coated. Let the mixture sit for about 10 minutes to allow the juices to develop.
Roll out one pie crust and fit it into a 9-inch pie pan. Pour the peach mixture into the crust, spreading it evenly. Dot the filling with small pieces of butter.
Roll out the second pie crust and place it over the filling. Seal the edges by crimping with your fingers or a fork. Cut several slits in the top crust to allow steam to escape. Brush the top crust with the beaten egg for a golden finish.
Bake in the preheated oven for 15 minutes. Reduce the temperature to 350°F and continue baking for an additional 30-35 minutes, or until the crust is golden brown and the filling is bubbly.
Allow the pie to cool for at least 2 hours before slicing to let the filling set.