- 1 1/2 cups red wine vinegar
- 1 cup water
- 2 tablespoons sugar
- 1 tablespoon kosher salt
- 6 whole cloves
- 2 bay leaves
- 1 teaspoon ground black pepper
- 1 teaspoon dried oregano (preferably Mexican)
- 1/4 teaspoon dried red pepper flakes
- 2 large red onions, thinly sliced
- Combine all ingredients except the onions in a heavy medium saucepan and set it over medium-high heat.
- Bring the mixture to a boil, then add the onion slices, separating them into individual rings. Let the mixture come back to a boil, then reduce the heat and cook until onions soften and wilt, 3 to 4 minutes.
- Remove the saucepan from the heat, cover, and let the mixture cool completely.
- Transfer the onions and their pickling liquid to a quart-size glass jar or divide among Tupperware.
- Cover and refrigerate for up to 2 weeks in the refrigerator.