How to Make It
MAKE THE CAKE Preheat the oven to 350°. Line the bottom of three 8-inch round cake pans with parchment paper and spray with nonstick cooking spray. In a medium bowl, whisk the flour with the cocoa powder and kosher salt.
In the bowl of a stand mixer fitted with a paddle attachment, beat the sugar with the oil at low speed until well combined, about 2 minutes. At medium speed, add the eggs, one at a time, and beat until incorporated. Continue mixing at medium speed until the mixture is well combined, 3 minutes longer. Reduce the mixer speed to low and slowly add the red food coloring and vanilla, mixing until the batter is evenly red, about 2 minutes. At low speed, alternately beat in the dry ingredients and buttermilk until just combined.
In a small bowl, mix the vinegar with the baking soda. Scrape the vinegar mixture into the cake batter and continue beating at low speed until the just combined.
Divide the cake batter among the prepared pans and bake for 35 minutes, until the cakes are springy to the touch and a toothpick inserted in the centers comes out clean. Transfer to a rack; let cool in the pans for 30 minutes. Invert the cakes and remove them from the pans; peel off the parchment and let cool completely. Place 1 cake layer on a cake stand or serving platter.
MEANWHILE, MAKE THE FROSTING In the bowl of a stand mixer fitted with a paddle attachment, beat the cream cheese with the butter at medium speed until smooth, about 2 minutes. Beat in the vanilla and confectioners' sugar, then beat at high speed until the frosting is light and fluffy, about 3 to 4 minutes more.
Using an offset spatula, scrape about 1 cup of the frosting onto the cake layer on the stand and spread it to the edge. Top with a second cake and spread 1 more cup of frosting on top. Invert the third cake layer on top so the flat side is up. Spread the remaining frosting over and around the side of the cake to cover completely. Refrigerate the cake for at least 2 hours before serving.