To make the sauce:
1. Heat oil in a heavy-bottomed saucepan over medium heat. Add onions, green pepper, and garlic. Cook, stirring, until onions are translucent, about 5 minutes. Add mushrooms and continue to sauté until mushrooms are soft. Add tomato sauce, tomatoes, Worcestershire, honey, and lemon juice and bring to a simmer; cook for about 5 minutes. Season with salt and pepper.
To make the fish:
1. Heat oven to 375°. Rinse fish inside and out with cold water and pat dry. Rub inside of cavity with a generous amount of sea salt and a little freshly ground black pepper. Stuff cavity with fresh herbs. Place in a greased baking pan and sprinkle lightly with sea salt and black pepper. Pour the Spanish sauce over and around the fish. Bake for 25–30 minutes, basting every 10 minutes with sauce from the pan, until fish is tender and flakes easily.
2. When done, gently push sauce from the top of the fish and spread two tablespoons of softened butter mixed with one tablespoon flour across the fish. Broil 3–4 minutes to brown the top of the fish. Serve garnished with lemon slices and parsley. A warm loaf of crusty Cuban is a perfect accompaniment.