In a large, heavy cast-iron pot, heat the oil. Add the flour, stirring constantly over low heat for 30 minutes to make a deep brown roux. Immediately add the onion, green onions, bell pepper, garlic, celery and stir until wilted, about 10 minutes. Add the red wine and the tomatoes. Stir to blend, and then let bubble for three minutes. Add the parsley, bay, thyme, allspice, salt, peppers, and lemon juice, and 2 cups of water. Stir to mix well, bring to a boil, lower the heat and let simmer for 30 minutes. Stir often, scraping the bottom of the pot to prevent the mixture from burning. If necessary, add some water, but the sauce should be thick and spicy.
Add the fish slices and lemon slices to the mixture and continue to cook at a simmer for 8 to 10 minutes. Serve in soup bowls over rice.
Makes 4 servings