Preheat oven to 400 degrees. Prepare crust, put bottom crust in pan.
Combine cherries with cornstarch, tapioca, salt, vanilla and mix. Pour into pan and press fruit to settle. Dot with chunks of butter. Lay in top crust and cut vents in with tip of sharp knife.
Bake at 400 degrees for 10 minutes. I recommend a baking sheet underneath to catch the run over. Reduce and bake additional 40 -50 minutes. Do NOT under bake or pie will not thicken. The pie should bubble and run over for at least 10 minutes. That's how you know it's done.
Allow to cool at least 1 hour before slicing if you want it to hold together. You may not. Hot runny pie has its own charms.