14+ Natural Red Food Dye Red Velvet Cake UK. I found some naturally dyed sprinkles at williams sonoma as well. If your beets came with the leaves still attached, slice them off at the base.
Some people told me that beets were traditionally used to colour the batter, while almost all of the recipes by famous chefs in the culinary/internet world used.
This hibiscus food coloring powder is an option too, although it's more pink than red. These days the sponge is most likely to be coloured using food colouring but there was also a trend during times of rationing to add vegetables to cakes, and beetroot was often added for its natural dyeing properties. Red velvet cake is a classic. On another topic, the history of red velvet cake was slightly interesting to me.