Preheat oven to 325 degrees.
Line the bottom of an 8-inch-square baking pan with a baking pan liner or lightly spray with vegetable cooking spray.
Sprinkle with flour.
Sift flour, baking powder, cinnamon, ginger, cloves, and salt together in a mixing bowl.
Combine prune puree, applesauce, or mashed banana and sugar in a separate bowl.
Stir in 1/2 teaspoon of the baking soda and molasses.
Add the remaining 1/4 teaspoon baking soda to the boiling water.
Alternate adding the prune puree mixture and the boiling water to the flour mixture, stirring to combine.
Add the egg whites and raisins.
Transfer cake batter to the baking pan.
Bake for 30 minutes or until a wooden pick inserted in center of the cake comes out clean.
Remove from pan and cool on wire rack.
Cut into 8 squares.