In large mixing bowl cream shortening, sugar, salt and vanilla. Add eggs and beat with mixer until mixture is very light and creamy. Add flour and buttermilk and beat 2 more minutes. In small mixing bowl mix cocoa, soda and hot water. Add to rest of batter. Put into a well geased and floured 13x9 inch pan. Bake at 350º for about 40-45 minutes. Frost with your favorite frosting.