Preheat oven to 350°.
Place cherries in greased 2 qt. baking dish.
Sprinkle 1/4-1/2 c. sugar over cherries.
Sprinkle tapioca over cherries.
In a medium bowl, cream butter and 1 c. sugar together.
Stir in flour.
Add egg and vanilla. Mix well.
Spoon mixture over cherries.
Bake for 35-45 minutes or until light brown on top.