In a large bowl, combine the first four ingredients; cut in butter until the mixture resembles coarse crumbs. Press into a greased 13-in. x 9-in. baking dish. Bake at 375° for 15 minutes.
Meanwhile, in a large bowl, beat eggs and sugar until thick and lemon-colored, about 5 minutes. Stir in flour, almonds, orange peel and baking powder. Arrange plums over crust; pour egg mixture over plums.
Combine the first three topping ingredients; sprinkle over filling. Top with almonds. Bake for 40-45 minutes or until golden brown. Yield: 12 servings.