- 1/2 cup apple cider vinegar
- 1 tablespoon sugar
- 1 1/2 teaspoons kosher salt
- 1 red onion, thinly sliced
- Whisk first 3 ingredients and 1 cup water in a small bowl until sugar and salt dissolve. Place onion in a jar; pour vinegar mixture over. Let sit at room temperature for 1 hour. DO AHEAD: Can be made 2 weeks ahead. Cover and chill. Drain onions before using.