For The Cake, Place A Rack In The Center Of The Oven, And Preheat The Oven To 350°F.
Grease Three 9″ Round Cake Pans, And Dust Them With Cocoa Or Flour.
Shake Out The Excess Cocoa Or Flour, And Set The Pans Aside.
Place The Butter And Sugar In A Large Mixing Bowl, And Beat With An Electric Mixer On Medium Speed Until Light And Creamy, 3 Minutes.
Add The Eggs, One At A Time, Beating Well After Each Addition.
Blend In The Vanilla And Red Food Coloring.
Set Aside.
In A Separate Bowl, Stir Together The Flour, Cocoa, And Salt.
In A Small Bowl, Stir Together The Buttermilk, Vinegar, And Baking Soda.
Add The Dry Ingredients And The Buttermilk Mixture To The Batter Alternately On Low Speed, Beginning And Ending With The Dry Ingredients.
Scrape Down The Bowl, And Stir To Blend The Batter One Last Time.
Divide The Batter Between The Pans, And Place The Pans In The Oven.
Bake The Cakes Until They Just Begin To Pull Away From The Sides Of The Pan, 16 To 18 Minutes.
Remove The Pans From The Oven, And Place Them On A Wire Rack To Cool For 10 Minutes.
Run A Knife Around The Edges Of The Pans, Give Them A Shake To Loosen The Cakes, Then Turn The Layers Out Once And Then Again Onto The Rack So They Cool Right Side Up.
While The Cakes Cool, Make The Ermine Frosting.
Whisk Together The Flour And Milk In A Small Saucepan Over Medium Heat Until It Is Very Thick And Puddinglike, 4 To 5 Minutes.
Remove The Pan From The Heat, And Whisk In The Vanilla And Salt.
Pour The Mixture Into A Small Heatproof Bowl.
Cover The Surface Of The Mixture With Plastic Wrap And Place In The Refrigerator To Cool For 1 Hour.
Place The Butter And Sugar In A Large Mixing Bowl, And Beat With An Electric Mixer On Medium Speed Until Light And Fluffy, 4 Minutes.
Remove The Milk And Flour Mixture From The Refrigerator, And Slowly Add It To The Butter And Sugar While Beating On Medium.
Continue To Beat Until The Mixture Is Light And Fluffy And Resembles Whipped Cream, About 2 Minutes.
To Assemble The Cake, Place 1 Layer On A Cake Plate.
Spread About ¾ Cup Of The Frosting Evenly To The Edges.
Place A Second Layer On Top And Repeat.
Place The Third Layer On Top, And Spread A Thin Layer Of Frosting On The Sides And On Top, Making What Is Called A Skim Coat.
Chill The Cake For 15 Minutes.
(This Seals In The Crumbs And Prevents Them From Being Dragged Into The Frosting And Turning The Frosting Pink.)
Remove The Cake From The Refrigerator And, With The Remaining Frosting, Frost The Top And Sides Of The Cake.
Slice And Serve.
