Beat sugar and margarine at medium speed of a mixer until well-blended (about 5 minutes). Add buttermilk, vanilla, and egg whites; beat well. Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 5 ingredients (flour through salt); gradually add to sugar mixture, beating just until blended. Stir in carrot and raisins.
Pour batter into an 11 x 7-inch baking dish coated with cooking spray. Bake at 350° for 33 minutes or until a wooden pick inserted in center comes out almost clean. Cool in pan on a wire rack.