For 2 cups Essential Simmered Tomato-Habanero Sauce:
3 medium-large round or 9 to 12 plum tomatoes
1+1/2 T vegetable or olive oil, plus a little more for oiling the baking dish
1 small white onion, finely sliced
1 to 2 fresh habanero chiles, stems removed and halved
Salt, about 3/4 t
For the fish:
1/4 c fresh sour orange juice or 2 to 3 T fresh lime juice
2 T roughly chopped epazote (or cilantro), plus a few sprigs for garnish
4 x 150gm fish steaks or boneless, skinless fillets (choose a fish that's still moist when cooked through, such as snapper, halibut, mahimahi, grouper or sea bass)
Making 2 cups of Essential Simmered Tomato Habanero Sauce:
Roast the tomatoes on a baking sheet 4 inches below a very hot broiler until blackened on one side, about 6 minutes, then flip and roast the other side. Cool, then peel, collecting all the juices with the tomatoes. Coarsely puree the tomatoes (with juices) in a food processor or blender.
In a deep, heavy skillet or medium-size saucepan, heat the oil over medium. Add the onion and fry until beginning to brown, about 6 minutes. Increase the heat to medium-high, and when quite hot, add the tomatoes and chile. Stir for about 5 minutes as the mixture sears and boils rapidly, then reduce the heat to medium-low and simmer for about 15 minutes, until medium thick. Season with salt.
Baking the fish:
Turn on the oven to 180c. Lay out the fish fillets in a lightly oiled baking dish without crowding them. Drizzle with the sour orange or lime juice and sprinkle with the epazote (cilantro). Spoon the warm tomato sauce over the fish, cover with foil and bake until the fish just flakes when pressed firmly, 10 to 15 minutes, depending on how thick the fillets are. With a spatula carefully transfer the fillets to a warm serving platter, thoroughly mix the sauce and juices that remain in the baking dish, then spoon them over the fish. (If the sauce seems too juicy, scrape it into a saucepan and boil it down; if too thick thin with a little water or broth; taste it and add more salt if necessary.) Garnish with sprigs of epazote (or cilantro) and serve at once.