- 1/2 small head of red cabbage, coarsely chopped
- 1/2 cup sugar
- 1/2 teaspoon baking soda
- Bring cabbage and 3 cups water to a simmer in a medium saucepan over medium-low heat and cook until cabbage is soft and liquid is reduced by about a third, 20–25 minutes.
- Remove cabbage with a spider or slotted spoon; discard. Add sugar to cabbage liquid and simmer, swirling pan occasionally, until liquid is a very deep purple and has reduced to about 1 cup, 10–15 minutes. Let dye cool, then stir in baking soda. Mix into frosting or royal icing to make desired color.