Serves 4

Onion confit is another name for sliced onions cooked long enough to turn golden brown, very tender, and delightfully sweet. The sweetness comes from the onions' natural sugars, which caramelize as they brown (they're also called caramelized onions). The confit makes a nice bed for roasted fish, in this case, fillets of salmon scented with orange and thyme. Serve the fish with small potatoes, steamed and tossed in butter.

7medium yellow onions (2 1/2 pounds)
2tablespoons olive oil
1tablespoon unsalted butter
1clove garlic, finely chopped
5 small sprigs fresh thyme
Salt and pepper, to taste
2tablespoons white wine vinegar
4 pieces skinless boneless salmon (1 1/2 to 2 pounds total)
Olive oil (for sprinkling)
2teaspoons finely grated orange rind
1tablespoon fresh thyme leaves
1tablespoon chopped fresh parsley

1. Trim the tip and hairy part of the root ends from the onions. Leave the roots intact (they hold the onions together). Peel and halve them lengthwise, from tip to root end. Lay them cut sides down on a cutting board. Cut crosswise into 1/4-inch slices.

2. In a large skillet with a heatproof handle over medium heat, heat the 2 tablespoons of oil. When it is hot, add the butter. When the butter melts, add the onions, garlic, thyme sprigs, and a generous pinch each of salt and pepper. Stir well. Cover the skillet and cook, stirring several times, for 15 minutes, or until the onions are tender (they won't be brown at this point).

3. Uncover the skillet and continue cooking the onions, stirring often, for 20 to 30 minutes, or until they are golden brown. Stir in the vinegar, scraping to deglaze the pan and loosen the darker caramelized bits. Remove from the heat and discard the thyme sprigs. (Total onion cooking time is 45 minutes.)

4. Set the oven at 400 degrees.

5. Place the salmon fillets, skinned side down (slightly rounded side up), on the onions. Sprinkle the salmon with olive oil, salt, pepper, orange rind, and thyme leaves.

6. Transfer to the oven and roast the salmon for 8 to 12 minutes, or until it is just cooked through (a meat thermometer will register 145 degrees; you can also insert the tip of a knife into the center and if the fish is opaque and still moist, it's done.)

7. Sprinkle with parsley and serve the salmon on the onion confit.

Lisa Zwirn