Preheat oven to 350 F. Lightly grease and flour three 8 or 9 inch round cake pans.
Sift together flour, cacao powder, baking soda and salt.
In a separate medium bowl, combine the buttermilk, vinegar, vanilla and red gel.
In a stand mixer, fitted with a paddle attachment, beat together the butter, oil and sugar on medium high speed, until smooth and fluffy - about 2 minutes. Add the eggs, one at a time, beating until fully combined after each addition. With the mixer on low speed, beat in the flour mixture in two to three additions, alternating with the red buttermilk mixture. Use a rubber spatula to scrape down the sides of the bowl as you go.
Divide the batter evenly among the three pans. Bake for 20 minutes or until toothpick comes out clean. Cool in the pans for 15 minutes and then turn over onto wire rack to allow to completely cool prior to icing.
Frosting:
In a stand mixer, fitted with a paddle attachment, beat the cream cheese, butter, vanilla and salt until smooth, about 2 minutes. Add the powdered sugar and mix on low until fully combined. Then, increase to medium high speed and beat for 2 more minutes until creamy, smooth and fluffy.
For this cake, spread about 1.5 cups per layer. I did not do the sides because I wanted to show the beautiful red cake. But you can do the sides - there is definitely enough frosting.