2 lb. skin-on kingfish or swordfish filets
Kosher salt and freshly ground black pepper, to taste
¼ cup fresh lime juice
2 tsp. ground cumin
5 cloves garlic, minced
6 green plantains, plus 2 ripe plantains, peeled and cut into 2" pieces
7 cups coconut milk
½ tsp. ground annatto seed (available at Spicesforless.com)
6 sprigs culantro or cilantro, chopped
4 large basil leaves, chopped
½ small yellow onion, minced
Season fish with salt and pepper and place in a large resealable plastic bag; add juice, 1 tsp. cumin, and garlic, and toss to combine. Seal bag, and let marinate in the refrigerator for at least 1 hour.
Place all plantains in a 6-qt. saucepan of salted water; bring to a boil over high heat. Reduce heat to medium-low; cook until tender, about 12 minutes. Drain; transfer to a food processor. Season with salt and pepper; purée until smooth, about 5 minutes. Transfer to a bowl and keep warm.
Bring coconut milk and 1 cup water to a boil in a 6-qt. saucepan over high heat. Reduce heat to medium, add remaining cumin, annatto, culantro, basil, and onion; cook until onions are soft, about 10 minutes. Add fish along with marinade; cook until fish is tender, about 8 minutes. Ladle soup into bowls and serve alongside plantain mixture.