Ingredients:
1 large red onion, thinly sliced
1 cup white vinegar
1/2 cup water
1 tablespoon granulated sugar
1 1/2 teaspoons salt
Optional additions:
1 clove garlic, sliced
1 teaspoon whole black peppercorns
1/2 teaspoon crushed red pepper flakes
1/2 teaspoon mustard seeds
