1. Heat the oven to 400 degrees F. Combine fruit with sugar and tapioca and set aside for 10 minutes or so.
2. Roll out 2 crusts and use one to line a 9-inch pie dish. Turn filling into crust and dot surface with butter.
3. Cover with the second crust and seal edges well, then cut several slashes to allow steam to escape. Bake until filling is bubbling and crust is nicely browned, about 40 minutes.