In a bowl, season the fish with half the garlic, the lime juice, salt and black pepper.
Heat a pot and coat it with olive oil. Add the onions, the rest of the garlic and cook for about 4 minutes in medium heat. Add the peppers and cook for about 5 minutes more or until the vegetables begin to get soft. Turn down the heat.
Take half the vegetables out of the pot and reserve as a side. Spread the remaining vegetables, add a layer of tomato slices on top, layer the fish, the rest of the tomatoes, the reserved vegetables and the chili, if using.
Add the coconut milk and salt, cover the pot and cook at medium heat until it comes to a boil. Turn down the heat, add the palm oil and cook for about 5 minutes. (Or until the fish is cooked.) Then, add, the cilantro and cook for 2 more minutes.
While the fish is cooking, heat a frying pan, add some olive oil and fry the plantain slices until browned on each side. Set aside as a garnish for the moqueca.
Dish the moqueca, garnish with some plantain slices and sprinkle with diced cilantro. Serve with white rice.