Preheat the oven to 350°F (175°C). Lightly grease a 9×13-inch baking pan with non-stick spray. For easier removal, line the bottom with parchment paper if desired.

In a large bowl, sift together the all-purpose flour, cocoa powder, baking soda, and salt. Set the mixture aside.

In a separate large bowl, use an electric mixer to beat the softened butter and granulated sugar until light and fluffy, approximately 3 to 4 minutes. Scrape down the sides and bottom of the bowl as needed to ensure even mixing.

Incorporate the eggs one at a time, beating well after each addition. Add the buttermilk, sour cream, vanilla extract, and enough red food coloring to achieve the desired shade. Beat on low speed until the mixture is smooth and combined.

Gradually add the dry ingredients to the wet ingredients. Mix on low speed or by hand with a spatula until no visible streaks of flour remain. Avoid overmixing.

Pour the batter into the prepared baking pan, spreading it evenly. Bake for 25 to 30 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. Allow the cake to cool completely in the pan on a wire rack.

While the cake cools, prepare the frosting. In a large bowl, beat the cream cheese and butter together until smooth and lump-free. Add the vanilla extract and salt; beat again until well incorporated.

Add 3 cups of sifted powdered sugar to the cream cheese mixture. Mix gently by hand until the powdered sugar is absorbed, then beat with an electric mixer until smooth. Add additional powdered sugar, 1/4 cup at a time, if a thicker consistency is preferred.

Once the cake is completely cool, spread the cream cheese frosting evenly over the surface. For best results, chill the cake for 20 to 30 minutes before slicing and serving.