Preheat your oven to 350 degrees and coat a bundt pan very generously with butter or a non stick baking spray that contains flour.
In a large bowl, whisk together the cake flour, baking soda, salt, and cocoa powder. Set aside.
Beat together the sugar and butter until light and fluffy, about three minutes. Make sure that you scrape the bowl down so all of the butter gets well combined with the sugar.
Beat in the eggs one at a time. Then add the yolks one at a time. Beat in the sour cream, scrape down the sides, then beat in the buttermilk. Then beat in the vinegar, vanilla, and food coloring one at a time.
Add in the flour mixture and turn the mixer on very low to just begin to combine. Then turn the mixer on high to finish. Beat until just combined, being careful to not overmix.
Pour the batter into the prepared bundt pan. Bake for 55 minutes or until a toothpick comes out with just a few crumbs. Be careful not to overbake.
Let it cool in it's pan for 15 minutes. Use a toothpick to loosen it gently from the sides. Gently flip it onto a cooling rack and let it cool there completely.
While the cake is cooling, beat together the cream cheese, powdered sugar, and buttermilk. Once the cake has cooled, spoon the frosting over it. You may not use all of the frosting.