Lemon-Baked Sea Bass with Spinach Salad

4 lemons
1 tablespoon minced shallot
2 tablespoons finely chopped fresh flat-leaf parsley
About 1 cup extra virgin olive oil
4 sea bass fillets, about 6 ounces each and 3/4 inch thick (if thicker, butterfly)
Gray salt and freshly ground pepper
2 tablespoons red onion slivers (see Chef's Note)
2 cups packed baby spinach

Preheat the oven to 450 F. Squeeze the juice of 2 lemons into a non-reactive baking dish and whisk in the shallot, parsley, and about 3/4 cup of the olive oil. Taste for balance; it should taste moderately tart. Add another 1 to 2 tablespoons olive oil, if necessary. Add the fish to the marinade and turn to coat well. Leave to marinate for 10 minutes.

Fold 4 large sheets of parchment paper in half. Beginning at one end of the fold, cut a point, then around into as wide a semicircle as possible, ending at the opposite end of the fold with a rounded point. When opened out, the paper will resemble a heart. Center the fish on one side of the heart, season with salt and pepper, and spoon a generous tablespoon of marinade over each fillet. Using a very sharp knife or mandoline, cut 1 lemon into very thin slices. Overlap 3 or 4 lemon slices along the length of each fillet.

Seal the packets and transfer them to a baking sheet. Bake in the preheated oven until cooked through, about 12 minutes, depending on the thickness of the fillets.

While the fish bakes, make the spinach salad. In a bowl, soak the red onion slivers in the juice of the remaining lemon for several minutes. The onions will turn a pale pink. Whisk in the remaining 1/4 cup olive oil and season to taste with salt and pepper. Add the spinach and toss well.

Variation : Fennel is classic as a flavoring for fish. Try adding a pinch of fennel spice to the marinade mixture.

Cut the onion in half lengthwise, and cut each half in half again crosswise. Cut the slivers lengthwise from each half. They will have an attractive crescent shape. You can also simply cut the onions into 1/4-inch dice.

When the fish is done, remove from the oven and place on 4 warm dinner plates. Cut open the packets and spread back the paper. Quickly divide the salad among the packets. The spinach will wilt across the top. Serve immediately.

Serves: 4