Cake: Cream shortening and sugar till fluffy. Add eggs and beat 1 minute. Add salt, beat. Add vanilla and coloring to buttermilk. Alternate adding flour and milk mixtures to batter. Combine soda and vinegar in cup and add to cake batter. Bake in (2) 9" cake pans at 350 deg for 25 to 30 min. Cool on cake racks. Frosting: Cook milk and flour till thick; cool in fridge. Beat butter , sugar and vanilla with mixer.
Add flour and milk mixture a little at a time (make ahead of cake so that it has plenty of time to cool).
