1. To prepare dressing, combine all ingredients; divide in half. Add 1 tablespoon salt to the half that you will be using as a marinade. Marinade the chicken for at least 2 hours and up to 12 hours.
2. Add oil to a skillet over medium-high heat. Add red onion and sauté 5 minutes until browned. Reduce temperature to medium-low and continue cooking, stirring occasionally, about 20 minutes more.
3. Discard marinade reserving chicken. Grill or sauté chicken on high heat for about 3 minutes on each side or until done.
4. To assemble salad, toss remaining ingredients together, top with the chicken and caramelized onions. Drizzle with dressing.