Banana Sour Cream Cake

1/4 cup light margarine

1/4 cup prunes -- pureed

1 1/4 cups sugar

1 egg

4 egg whites

2 1/2 cups flour

3/4 teaspoon baking powder

3/4 teaspoon baking soda

1/2 teaspoon salt

1 1/4 cups mashed bananas -- about 3

1/2 cup nonfat vanilla yogurt

Cream margarine and sugar well. Add egg and egg whites and beat well. Combine flour, baking powder, baking soda and salt. Add to sugar mixture and beat until mixed. Add banans and yogurt and blend well. Put in a 13"x9" greased baking pan and bake at 350 degrees for 40-45 mins or until a cake tester comes out clean.Cool on a rack.