Thaw cherries until most of the free ice has disappeared. Drain off juices, measure and stir into mixture of sugar, tapioca and cornstarch in saucepan. Heat rapidly until thickening is complete. Boiling is not necessary. Set aside to cool.
Add cherries and lemon juice to cooled, thickened juice. Pour filling into pastry-lined 9" pie pan. Cut vents and adjust top