Dry the skin of the mackerel as well as you can, and season the flesh with oil, salt and pepper. Set aside to air dry for a few minutes while you prepare the sauces
Blend all the ingredients for the marinade together to a fine paste
Char the onion, garlic and jalapeño for the green sauce over a grill until blackened and then set aside
Blend all the ingredients for the green sauce together, adding water as needed, until it has the texture of pesto. Set aside in the fridge
Rub oil into the skin of the mackerel and spread the marinade on the meat
Grill the mackerel until cooked through, about 4 minutes per side
Serve with a slice of lemon or lime, and some green sauce on the side. Adriana serves hers with a grilled tomato, green salad or some rice. You can also enjoy it as a taco inside a tortilla