Cream butter and gradually add sugar, beating with an electric mixer at medium speed until smooth. Add eggs, one at a time, beating after each addition. Combine flour, baking soda and spices. Set aside. Combine molasses and sour cream. Add flour mixture to creamed mixture, alternating with molasses mixture, beginning and ending with flour mixture. Mix just until blended after each addition. Grease and flour 10 inch Bundt pan. Pour batter into pan. Bake at 325ºF.  for 1 hour until toothpick, inserted in center, comes out clean. Cool in pan 15 minutes; remove from pan and let cool completely on wire rack. Sift powdered sugar over cake. Serve with Lemon Sauce if desired. Lemon Sauce: Combine sugar, cornstarch and water; stir until smooth. Cook over medium heat, stirring until smooth and thickened. Add butter, lemon rind and juice. Cook until heated through, stirring constantly. Makes 1 1/3 cups.