How to Make It
Preheat oven to 350°.
Combine first 5 ingredients in a large bowl; cut in 1/2 cup margarine with a pastry blender or 2 knives until mixture resembles coarse meal. Place 1 cup flour mixture in a small bowl; cut in 2 tablespoons margarine to form a streusel; set aside.
Add baking powder and baking soda to remaining flour mixture in large bowl; stir well. Combine buttermilk, egg substitute, apple butter, vanilla, and lemon rind. Pour buttermilk mixture over flour mixture; beat at low speed of a mixer until well-blended.
Pour batter into a 13 x 9-inch baking pan coated with cooking spray. Top batter with blueberries, and sprinkle with reserved streusel. Bake at 350° for 50 minutes or until a wooden pick inserted in center of cake comes out clean. Let cake cool in pan on a wire rack.