Prepare the Dough: Roll the larger portion of dough into a 10-by-15-inch rectangle and transfer it to a baking sheet. Roll the smaller portion into a 13-inch round and transfer it to a 9-inch glass pie plate. Fold the excess dough over the edge to create a simple border. Cover both and refrigerate for at least 2 hours or up to 24 hours.
Prepare the Filling: If using fresh cherries, wash, pit, and optionally reserve the pits for whipped cream flavoring. Toss the cherries with lemon juice, sugar, salt, and tapioca flour in a medium bowl until evenly combined. Pour the mixture into the chilled pie shell and refrigerate.
Create the Lattice Top: Cut the chilled dough rectangle into thirty 10-by-½-inch strips. Lay the strips over the pie in a checkerboard pattern, folding back alternate strips to create a lattice. Trim the excess dough, tuck it under the edge of the crust, and refrigerate until firm and cold, at least 30 minutes.
Preheat and Prepare for Baking: Adjust the oven racks so one is in the lower-middle position and the other in the topmost position. Preheat the oven to 400°F.
Brush and Bake the Pie: Whisk together the egg, egg yolk, cream, and salt for the egg wash, then brush it over the pie. Bake on a parchment-lined baking sheet for 75 minutes or until the juices bubble in the center, with an internal temperature of 213°F. Halfway through, place an empty baking sheet on the top rack to shield the pie from over-browning.
Cool the Pie: Let the pie cool to 85°F before slicing (about 3 hours in a cool kitchen or up to 4 hours otherwise).
Serve: Slice and serve with dollops of Make-Ahead Whipped Cream. Leftovers can be stored for 3 days at room temperature or reheated in a 350°F oven for 10 minutes to restore crispiness.