Preheat the oven to 400°F.
In a medium bowl, mix the cherries, cornstarch, sugar, vanilla, and salt until the cherries are coated with the cornstarch mixture.
Gently press the bottom pie crust into a 9-inch pie dish, making sure that it is pressed against the edges and bottom with no gaps or air bubbles. Pour the cherry mixture into the bottom crust.
Roll out the top crust and cut into one-inch wide strips using a pizza cutter or a sharp knife. Lay half of the strips across the pie, spacing about ¼ inch apart. Fold every other strip back on itself, then lay one of the remaining strips across the middle of the pie, perpendicular to the previous strips.
Fold the strips back down over the new strip, Repeat, alternating which strips are folded back on themselves, until the top of the pie is covered in a lattice pattern.
Cut off the excess crust using a sharp knife. Pinch the bottom crust and top crust together to seal.
In a small bowl, whisk the egg yolk and water. Brush the egg wash over the top of the pie, and sprinkle with additional sugar if desired.
Bake for 55-60 minutes or until the filling is bubbling hard and the pie crust is golden brown. Let cool to nearly room temperature before slicing and serving.