Heat oven to 350° F. Grease and flour 13x9-inch baking pan.*
In medium bowl, combine flour, cocoa and salt; set aside.
Beat butter and sugar in large bowl; add eggs and vanilla, beating well.
Stir together buttermilk and food color.
Add flour mixture alternately to butter mixture with buttermilk mixture, mixing well. Stir in baking soda and vinegar. Pour into prepared pan.
Bake 30 to 35 minutes or until wooden pick inserted in center comes out clean. Cool completely in pan on wire rack.
Frost with White Mountain Frosting, or as desired.
Servings: 15