For the Cake, preheat oven to 350°F. Mix water and flaxseed in small bowl, let stand 15 minutes. Grease and flour 13x9-inch baking pan; set aside.
Mix flour, baking powder, baking soda, salt and spices in large bowl. Add remaining ingredients and flaxseed mixture; stirring well to mix. Pour into prepared baking pan.
Bake 35 minutes or until toothpick inserted in center comes out clean. Cool in pan on wire rack.
Meanwhile, for the Frosting, beat cream cheese, butter and vanilla in large bowl with electric mixer on medium speed until well blended. Gradually add confectioners' sugar, beating well after each addition. Frost cooled cake with Vanilla Cream Cheese Frosting. Top with additional chopped pecans, if desired. Cover any leftover cake and store in refrigerator.
Test Kitchen Tip: Prefer a layered cake? This recipe can be prepared using 2 (8-inch) round cake pans. Simply divide your cake batter evenly between the 2 greased and floured pans and bake as directed. Cool in pans 5 minutes. Remove from pans; cool completely on wire rack. Place one cooled cake layer on serving platter and spread with about 1/2 cup of the frosting. Top with second cake layer. Frost top and sides of cake with remaining frosting. Sprinkle with additional chopped pecans, if desired.