Spray a 11 x 7 x 1 1/2 inch baking pan with olive oil spray.
3
Rinse fish and pat dry with paper towels.
4
To assemble, spread spinach on pan, place fish onto spinach. Sprinkle with salt and pepper and top with tomato and onion slices. Drizzle with olive oil, vinegar and lemon juice.
5
Bake uncovered for 20 minutes until fish flakes easily when tested with a fork.