Preheat oven to 350°.
Heat 1 tablespoon oil in a large nonstick skillet over medium heat. Add onion; sauté 7 minutes or until tender. Add chopped tomato and next 5 ingredients (chopped tomato through garlic); reduce heat, and simmer, uncovered, 15 minutes or until liquid evaporates, stirring occasionally. Set aside.
Arrange fillets in a 13 x 9-inch baking dish coated with cooking spray. Sprinkle lemon juice and 1/2 teaspoon salt over fillets, and top with onion mixture. Place potato wedges over onion mixture, and drizzle with 1 tablespoon oil and 1/4 teaspoon salt. Top with tomato slices and bell pepper rings. Bake, uncovered, at 350° for 1 hour and 20 minutes or until potatoes are tender.
Place 1 fillet and 6 potato wedges on each of 8 plates. Divide onion mixture evenly among each serving, and top each serving with 1 tomato slice and 1 bell pepper ring.