Bring margarine, water and cocoa to a boil. Mix flour, salt and sugar in mixing bowl. Add the hot mixture and stir well. Add eggs and beat well. Then add sour cream, soda and vanilla. Put into a greased cookie sheet pan. Bake at 350 degrees for 25-30 minutes. Frost when done.
Heat sugar, margarine, milk and cocoa. Cool. Add remaining ingredients and stir till smooth. Frost cake when cool.