* 2 pounds lemon sole, grouper, red snapper, perch, or similar nonoily, fairly firm fleshed fish fillet (choose fillets no more than ½ inch thick).
* About 1 cup unbleached all-purpose flour
* Salt and freshly ground black pepper
* Olive oil, for frying, plus 2 tbsp additional
* 1 large. juicy orange, preferable thin-skinned, very thinly sliced
* 1½ pounds onions, very thinly sliced (6 cups)
* ¼ cup pine nuts
* ¼ cup raisins
* ½ cup balsamic or red wine vinegar
* 2 anchovies, finely chopped (optional).
* 1 cup orange juice
* 1 bay leaf
* Bright green leaves of parsley, curly endive, fris
1. Cut the fillet in half lengthwise and, if necessary, remove the thin bony strip that runs through the middle of many fillets. Now cut the fillet into 4-inch pieces. If time permits, soak the fish in a pan of cold, lightly salted water for about 20 minutes. (This centuries-old technique not only seasons the fish, but also helps it to stay firm when fired.)
2. Pat the fish dry with paper towels. Spread the flour on a sheet of wax paper or a platter and season with salt and pepper. Dredge the fish pieces thoroughly in the seasoned flour, then shake lightly to remove all excess. Heat ¼ inch of oil in a large heavy skillet until hot but not smoking. Fry the fish in batches until nicely golden on both sides. Drain well on paper towels.
3. Choose a casserole or nonreactive baking dish just large enough to accommodate the fish in one layer and line it with the orange slices. Place the fish on top, overlapping the pieces slightly if necessary.
4. Wipe out all the oil in the skillet, then warm the 2 tbsp of fresh oil in it. Add the onions and toss until completely coated with the oil. Salt and pepper lightly, cover the pan, and cook slowly over very low heat for 35-40 minutes, until the onions are meltingly tender. Stir from time to time to make sure the onions don't burn.
5. While the onions are simmering, toast the pine nuts on a baking sheet in a preheated 350 degrees F oven for 7-10 minutes, until fragrant and lightly golden. Shake the baking sheet from time to time to ensure even toasting. Set the toasted nuts aside to cool. Soak the raisins in the vinegar.
6. When the onions are very tender, stir in the optional anchovies (they add an elusive, subtle depth), and cook for 2 minutes, stirring to dissolve them. Add the vinegar with the raisins, the orange juice, and bay leaf. Turn the heat up to high and cook, uncovered, until the liquid is reduced by half and onions are caramelized and richly colored, 15-20 minutes. Be sure to stir frequently to redistribute the syrupy juices and , if necessary, turn the heat down a bit to prevent the onions from sticking and burning. Season generously with salt and peppr and remove the bay leaf.
7. Spread the caramelized onion mixture evenly over the fish. Scatter the toasted pine nuts on top. Wrap well with plastic and refrigerate for at least 6 hours or overnight (even better when served after 48 hours). It will keep very well for at least 4 days.
8. The fish is best at room temperature, so remove it from the refrigerator at least 1 hour before serving. Brighten the dish with a garnish of parsley, curly endive, fris