Serves 4
Calories per serving: 215

4 cod fillets (each 5 ounces, about 1 inch thick), any bones removed
1/2 teaspoon salt
1 onion, thinly sliced
1 red bell pepper, stemmed, seeded and thinly sliced
2 teaspoons olive oil
4 pitted Kalamata black olives, quartered
1/4 cup chopped fresh flat-leaf parsley
1/4 cup light mayonnaise
2 teaspoons Old Bay seasoning

1. Preheat the oven to 400 degrees. Place a rimmed baking sheet on the bottom rack.

2. Season the cod fillets with 1/4 teaspoon salt, then arrange each fillet in the center of a 15-x-12-inch piece of foil. Toss together the onion, pepper, oil and remaining 1/4 teaspoon salt in a medium bowl until evenly coated. Divide the mixture among the fish fillets. Top each with the olives and parsley.

3. Gather sides of foil over fish to form a pouch and crimp tightly, leaving no openings. Put packages on hot baking sheet and bake until fish is just cooked through, 18 to 20 minutes. To check for doneness, carefully open the packet, being careful of any escaping steam. Pierce the center of the fish with a knife; it should be opaque in the center.

4. Meanwhile, stir together the mayonnaise and Old Bay seasoning until well combined. Carefully open the fish pouches and serve with the Old Bay mayonnaise.