First make the pie filling. In a small mixing bowl, whisk together the granulated sugar, light brown sugar, salt and cornstarch. In a medium heavy-bottomed pan, combine the water and lemon juice over medium heat. Whisk the dry ingredients into the liquid in the pan. Bring the mixture to a simmer. Add in the cherries and bring to a boil. Reduce the temperature to a simmer and cook until the sauce is thickened and looks clear and not foggy, about 6-8 minutes. Stir in the lemon zest, remove from the heat and let cool.
Once the filling is almost cool, remove the pie dough from the refrigerator. On a lightly floured surface, roll out one piece of pie dough to a rough 12 inch circle. Place this dough in a 9" pie plate and gently press it into the corners of the plate. Place this in the fridge to re-chill while you roll out the next piece of dough. Roll this piece of dough into a rough 12" circle. Cut the dough into 1 1/2-2"wide strips to make a lattice top.
Remove the pie pan from the fridge. Pour the filling into the pie shell. Place 3-4 strips of your top dough vertically the pie. Then, place the remaining strips horizontally, one at a time lifting every other vertical strip to create a lattice topping.
For the finished edges, I like to use a traditional crimped edge. To do so, press gently all the way around the pie to be sure that the top and bottom crusts are sticking together. Trim the dough until there is just about an inch of dough all the way around. I like to use a pair of kitchen shears for this. Then, fold the dough up on itself all the way around. Using your thumb and fingers, crimp the edge all the way around the pie. Brush the pastry with the beaten egg and sprinkle with sugar. Place the pie in fridge for at least 30 minutes to let the dough chill back down. Preheat the oven 425 degrees Fahrenheit while the pie is chilling.
Place the pie on a foil lined rimmed baking sheet and bake at 425 degrees Fahrenheit for 45 minutes. Reduce the temperature to 375 degrees and continue to back for 15-30 more minutes. The pie is done once the top is golden and the cherry juices are bubbling.
Remove the pie from the oven and allow to cool on a wire cooling rack. At least 2 hours. I prefer to let it cool over night. The pie will keep for 2 days at room temperature or 4 days in the fridge. Serve with vanilla ice cream or whipped cream or just a drizzle of cream!
*I use demarara sugar because it gives the crust a nice crunch, but you can use granulated sugar if you'd like.