Taken from Diana Kennedy's book "The Essential Cuisines of Mexico."
A 3- 3.5 Pound Red Snapper
1 Scant teaspoon salt
freshly ground pepper
1.5 Cups thinly sliced white onions
1/3 Cup fresh lime juice
1/3 Cup Olive oil
3 Jalapeno chilies en escabeche
3 Tablespoons juice from the Chile can
2 Cups roughly chopped cilantro
Have the fish cleaned, leaving the head and tail on. Prick the fish all over with a coarse-tined fork, rub in the salt and and pepper. Place the fish onto a baking dish with half the onions underneath and the rest on top. Pour the lime juice over it and set it aside for about 1 hour, turning it over once during that time.
Preheat oven to 350 degrees.
Cover the dish and bake the fish for about 15 minutes on each side.
Add the rest of the ingredients and continue cooking the fish, covered, until it is just cooked, basting it from time to time with the juices in the dish - about 20 minutes.
Note: This dish is also delicious cold, if there is any left over.