Preheat oven to 350°.
Place granulated sugar and butter in a large bowl, and beat with a mixer at medium speed until well blended. Add pumpkin; beat well. Add egg substitute and vanilla; beat until well blended.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 6 ingredients (through nutmeg), stirring with a whisk. Add flour mixture and milk alternately to butter mixture, beginning and ending with flour mixture. Pour batter into 2 (9-inch) round cake pans coated with cooking spray; sharply tap pans once on counter to remove air bubbles. Bake at 350° for 30 minutes or until wooden pick inserted in center comes out clean. Cool in pans 10 minutes on a wire rack; remove from pans. Cool completely on wire rack.
Place 1 cup powdered sugar and cream cheese in a large bowl; beat with a mixer at medium speed until well blended. Add remaining powdered sugar and rind; beat until fluffy.
Place 1 cake layer on a plate. Spread 2/3 cup cream cheese frosting evenly over top of cake. Top with remaining cake layer; spread remaining cream cheese frosting over top, but not sides, of cake. Arrange orange slices in a ring around outer edge of top cake layer. Sprinkle pomegranate seeds over center of top cake layer. Store cake loosely covered in refrigerator.