Preheat oven to 325°.
Place sugar and butter in a large bowl; beat with a mixer at medium speed until well blended (about 5 minutes). Gradually add egg substitute, beating well.
Combine sour cream and baking soda. Stir well, and set aside. Lightly spoon cake flour into dry measuring cups, and level with a knife. Combine flour and salt. Add flour mixture and sour cream mixture alternately to sugar mixture, beginning and ending with flour mixture. Stir in vanilla.
Pour batter into a 10-inch tube pan coated with cooking spray. Bake at 325° for 1 hour and 35 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes on wire rack; remove from pan. Cool completely on wire rack. Garnish with blackberries and mint, if desired.
Note: Eight egg whites can be used in place of egg substitute. Add one at a time to sugar mixture.
Lemon: Add 1 teaspoon grated lemon rind.
Coconut: Decrease vanilla to 1 teaspoon; add 1 teaspoon coconut extract.
Almond: Decrease vanilla to 1 teaspoon; add 1 teaspoon almond extract.