Take a small nonstick skillet heated to meddium high heat and coat with cooking spray. Add lemon, 1 tbls. water, 1/2 teaspoons oil, and sugar and cook 3 minutes or until water evaporates and mixture just begins to brown, stirring frequently. Set aside.
Put remaining 2 1/2 tsps. oil in a small microwave safe bowl. Microwave at High for 10 seconds, just until oil is heated. Add saffron and let stand 10 minutes.
Combine lemon mixture, saffron mixture, chopped parsley, cilantro, salt, paprika, cumin, black pepper, olives, and garlic cloves in a large zip lock plastic bag. Add fish to bag and seal. Marinate in refrigerator 30 minutes, turning occasionally.
Preheat oven to 400*F.
Saute the onions in the 1 tbls. olive oil for a few minutes to bring out the flavor.
Layer 1 cup of the onion slices and 2 cups tomatoes on the bottom of a 13"x9" baking dish coated with cooking spray. Take the fish out of bag, reserving marinade. Top tomato with fish; pour remaining marinade from bag over fish. Cover with remaining 2 cups tomatoes and remaining 1 cup onion. Cover with foil. Bake at 400*F. for 40 minutes or until fish flakes easily when tested with a fork. Remove from oven.
Move fish and vegetables to a serving platter. Drizzle remaining liquid over fish.
Garnish with cilantro leaves, if desired. Serve immediately. Enjoy!