Preheat oven to 350°.
Lightly spoon flour into dry measuring cups, and level with a knife. Combine the flour and next 5 ingredients (flour through ginger) in a large bowl, and cut in margarine with a pastry blender or 2 knives until mixture resembles coarse meal. Remove 3/4 cup flour mixture, and place in a small bowl. Stir in pecans; set pecan mixture aside. Add baking powder, baking soda, and salt to remaining flour mixture, and stir in pear. Combine sour cream, vanilla, lemon rind, egg, and egg white; stir well with a whisk. Add to flour mixture, stirring just until moist. Pour cake batter into a 13 x 9-inch baking pan coated with cooking spray, and top with pecan mixture. Bake at 350° for 50 minutes or until a wooden pick inserted in center comes out clean. Cool in pan on a wire rack.