Preheat oven to 400°.
Combine first 10 ingredients in a large bowl. Add salmon, turning to coat. Cover and let stand 15 minutes. Remove salmon from bowl, reserving marinade. Place the salmon, skin side down, in a 13 x 9-inch baking dish coated with cooking spray.
Cut lemon in half lengthwise; cut 1 lemon half crosswise into 1/8-inch-thick slices. Reserve remaining lemon half for another use. Add the lemon slices, red and green bell pepper slices, 2 tablespoons water, and tomato slices to marinade; stir gently to coat. Arrange lemon mixture in an even layer over salmon; cover with foil. Bake at 400° for 20 minutes or until fish flakes easily when tested with a fork or until desired degree of doneness.
Place 1 fillet on each of 4 plates. Top each serving with about 1/2 cup lemon mixture, and drizzle each serving with about 2 1/2 tablespoons pan juices.