1. Place fish in a shallow non-reactive (non-metal) bowl. Combine the tomatoes, onion, cilantro, garlic, chile pepper, lime juice, oil and salt in a food processor fitted with the metal blade (or a blender). Process until smooth and pour over fish. Allow to marinate for 30 minutes to 1 hour.
2. Heat 1 tablespoon coconut oil or olive oil in a large skillet over medium heat. Add diced sweet potato and cook for 10-15 minutes, adding a little water if needed so it doesn't burn, until softened. Add zucchini, green and red pepper and continue to cook until tender, about 5-7 minutes, again adding water to the pan, if needed. Add water or fish stock and stir in coconut milk. Bring to a boil, reduce heat, and simmer 2 to 3 minutes.
3. Add fish and marinade and simmer for 10-15 minutes, or until fish flakes easily with a fork. Just before serving, stir in green onion and cilantro. Serve over brown rice, quinoa, or another healthy whole grain, if desired.