Preheat the oven to 335°F (170°C). Coat three 8-inch round cake pans with grease and line them with parchment paper.

Mix the dry ingredients – In a large mixing bowl, combine the cake mix, flour, sugar, cocoa powder, salt, and baking soda. Mix on low until combined.

Add the wet ingredients – Add the vanilla extract, melted butter, oil, buttermilk, sour cream, and eggs to the dry mix. Mix on low for 2 minutes, scrape the bowl, and mix again on medium until smooth.

Add the food coloring – Mix in the super red food coloring until the batter is evenly colored.

Bake – Pour the batter evenly into the prepared cake pans. Bake for 25 to 30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs attached.

Cool – Let the cakes cool in the pans for 5 minutes before transferring to a wire rack to cool completely.

Whip the egg whites and sugar – In the bowl of a stand mixer, combine the egg whites and powdered sugar. Whip on low until combined, then whip on high for 1 minute.

Add the butter and flavoring – Gradually add the butter, one piece at a time. Add the vanilla and salt. Keep whipping until smooth.

Adjust the color – Add the yellow, pink, and red food coloring until you achieve a vibrant red hue.

Smooth the frosting – Switch to the paddle attachment and mix on low for 15 to 20 minutes to remove air bubbles.

Level the cake layers if needed.

Spread a layer of buttercream on the first cake layer.

Add the second layer and repeat the process.

Frost the top and sides with a crumb coat, chill for 15 minutes, then apply a final smooth layer of buttercream.

Decorate with cake crumbs, sprinkles, or chocolate shavings if desired.

For a more vibrant color and moist texture, use gel-based food coloring and brush the cake layers with simple syrup before frosting.