Beat shortening and sugar at medium speed with an electric mixer until fluffy. Add eggs, one at a time, beating just until yellow dissapears. Stir in vanilla and food coloring.
Combine flour, baking soda, salt and cocoa. Stir together buttermilk and vinegar; add to shortening mixture alternately with flour mixture, beginning and ending with flour mixture. Beat just until blended after each addition.
Pour batter into 2 greased and floured 9" round cakes; bake at 350° for 25 minutes or until a toothpick inserted in center comes out clean. Cool in pans on a wire rack 10 minutes; remove from pans. Cool completely on wire racks. Spread Best-Ever Soft Icing between layers and on top and sides of cake.
Best-Ever Soft Icing: Whisk together flour and milk in a small saucepan over low heat until thickened. Pour into mixing bowl; allow to cool. Add butter and remaining ingreidents to flour mixture; beat at high speed with an electric mixer until fluffy, about 8 minutes.