Servings: Makes 16 servings
Preheat oven to 350°. Lightly coat a 9-inch cake pan with cooking spray and dust with flour; set aside.
For the topping: In a mixing bowl, combine flour and sugar. Using a pastry blender or 2 knives, cut in butter until mixture resembles a coarse meal. Set crumb mixture aside.
To make the cake: In a medium mixing bowl, combine flour, sugar, baking powder, baking soda, salt, nutmeg and cherries; stir well and set aside. In a separate mixing bowl, combine buttermilk, orange zest, oil, prune puree, vanilla and egg whites; whisk until egg whites are well beaten. Gradually add flour mixture, stirring just until dry ingredients are moistened.
To assemble: Pour batter into the prepared cake pan and sprinkle crumb mixture over the batter.
Bake for 40 to 50 minutes, or until a wooden pick inserted in the center comes out clean. Cool in the pan on a wire rack.
Cut into 16 wedges. Serve warm or room temperature.