1. Preheat broiler.
2. Arrange tomato slices on a large baking sheet. Coat slices with cooking spray, and broil 3 inches from heat 6 to 8 minutes or until browned.
3. Position knife blade in food processor bowl; add tomato, vinegar, and next 3 ingredients. Process until smooth, stopping once to scrape down sides. Add capers, and set aside.
4. Prepare grill.
5. Coat grill rack with cooking spray. Place on grill over medium-hot coals (350° to 400°). Place fillets on rack; grill, covered, 4 to 5 minutes on each side or until fish flakes easily when tested with a fork. Transfer fillets to a serving platter; top evenly with vinaigrette.