Preheat oven to 350°F. For the Cake, grease 2 (9-inch) round cake pans with oil. Set aside. Mix cornstarch, sorghum flour, tapioca flour, xanthan gum, baking powder, baking soda and salt in medium bowl. Set aside.
Beat granulated sugar, oil, coconut milk and vanilla in large bowl with electric mixer on medium speed until well blended. Beat in eggs, 1 at a time. Gradually add flour mixture beating on low speed after each addition until smooth. Do not overbeat. Pour batter into prepared pans.
Bake 30 to 35 minutes or until toothpick inserted in center comes out clean. Cool in pans 10 minutes. Remove from pans; cool completely on wire rack.
For the Frosting, beat spread and vanilla in large bowl with electric mixer on medium speed until light and fluffy. Mix confectioners' sugar and cocoa powder. Gradually add to spread, beating until well blended after each addition and scraping sides and bottom of bowl frequently. Add coconut milk; beat until light and fluffy. Fill and frost cooled cake with Frosting.