Grease 3 (8-inch) round cake pans, and line bottoms with parchment paper.
With an electric mixer on high speed, cream butter, shortening and sugar for about 4-5 minutes until fluffy, making certain that no sugar granules remain in the creamed mixture.
Add in eggs and vanilla; blend well to combine.
Mix in sour cream and cocoa; blend well.
In a small bowl, blend the boiling water and food colouring together; set aside.
In a small bowl sift together cake flour with baking soda, baking powder and salt.
Add in the flour mixture alternating with the boiling water to the creamed mixture; mix to make a smooth batter.
Divide batter into prepared baking pans, and tap gently on the counter to remove any air bubbles in the batter.
Bake about 30-35 minutes, or until cake test done.