Put the flour and sugar into a food processor and pulse to combine
Add the butter cubes and pulse until the butter is distributed in small pieces into the flour, then add the water through the drip top while the blender is going. Give the blender about a minute to combine into a large dough ball. Depending on how dry it is, you may need to add some more splashes of water for it to come together.
Divide the dough into 2 disks, cover with plastic wrap, and let the dough chill in the refrigerator for an hour or 2. You can make the cherry pie filling while the dough chills.
Meanwhile, you can make the cherry filling. Combine the cherries, sugar, tapioca starch, and lemon juice in a sauce pan and bring to a simmer for 5 minutes, until the starch makes the cherry filling saucy and thickened.
When your dough has chilled, and you are ready to bake the pie, pre-heat the oven to 375 degrees.
Knead the dough for a minute to make it pliable to your warm hands, and roll out the bottom of the pie crust on a flour dusted surface. Put the bottom pie crust into your pie plate.
Roll out the second ball of dough and either slice strips for a lattice top, or use a cookie cutter to make pie crust shapes for the top.
Pour the cherry filling into the pie crust, and top with your crust topping.
Brush the top crust with egg wash, and sprinkle pure cane sugar.
Bake the pie on a cookie sheet at 375 degrees for 45-55 minutes, until the top crust is golden brown. Let the pie cool for at least an hour before slicing. It will keep for several days, so it could be made in advance too.