Ingredients

1. 1 1/2 cups white wine or cider vinegar
2. 1 1/2 cups cold water
3. 1 teaspoon sugar
4. 1/2 teaspoon salt
5. 1 large, dark red onion, sliced into 1/8-inch rounds
6. 3 cups boiling water

Directions

1. In a medium bowl, combine the vinegar and cold water with the sugar and salt. Stir to dissolve the sugar and salt.
2. Put the onion slices in a colander and pour the boiling water over them. Rinse under cool water and drain. Add the onion to the vinegar brine, cover with plastic wrap and refrigerate until chilled.

Make Ahead

The onions can be refrigerated for up to 1 week.