1. Brush onion slices with olive oil; cook in a hot grill pan over medium-high heat about 5 minutes on each side or until grill marks appear. Coarsely chop onion.
2. Toss together peas, chopped onion, and 3 Tbsp. Apple Cider Vinaigrette in a medium bowl. Gently toss together tomatoes, next 2 ingredients, and 3 Tbsp. Apple Cider Vinaigrette in another bowl.
3. Spoon rice onto a serving platter; top with tomato mixture and pea mixture. Serve with remaining vinaigrette.