Prepare crust, mix together:

2 cups sifted flour
2 T. sugar
1 tsp. baking powder

Rub in 6 oz. doftened butter until well incorporated.

Combine and add:

2 T. water
1 beaten egg
1 tsp. vanilla

Knead and press into a 10 inch fluted tart pan.
Press halved prune plums cutside up into pastry.
Dot plums with butter.
Sprinkle liberally with:

3/4 cup sugar
2 tsp. cinammon
1 tsp. cornstarch

Bake at 425 for 20-30 minutes.