Wiktionary
red velvet cake
n. A rich, sweet cake with a distinctive reddish colour.
Wikipedia
Red velvet cake
Red velvet cake is a chocolate cake with either a red, bright red or red-brown color. It is traditionally prepared as a layer cake topped with cream cheese or cooked roux icing.
Common ingredients include buttermilk, butter, cocoa, and flour for the cake, beetroot or red food coloring for the color.