*The store did not have Cod so I used Haddock. I also cut the recipe ingredients in about 1/3.
Marinate fish: In a small bowl, combine 1/4 cup olive oil, 1/2 teaspoon salt and1/2 teaspoon freshly ground black pepper. Rub marinade into 4 pounds cod fillets, skins removed. Cover with plastic wrap and refrigerate until ready to cook. Prepare vegetables: Preheat oven to 450 degrees. Remove stalks and outer layers from 3 large bulbs fennel, and cut bulbs lengthwise into 8 parts each (reserve fronds for garnish). In a large ovenproof skillet or flameproof roasting pan, toss cut fennel with 4 large red onions, cut into 8 wedges each, 1 head garlic, broken into cloves and peeled, 2 lemons, sliced into thin rounds and seeds removed, 2 teaspoons coriander seeds, 1 tablespoon whole fennel seeds and 1/2 cup extra-virgin olive oil. (Two skillets or pans can be used if necessary.) Place in oven and cook 25 minutes. Add 3 fairly hard pears, peeled, cored and cut into 4 wedges each, salt and freshly ground black pepperto taste and 1/4 cup fish stock (vegetable stock or water can be substituted) to skillet and continue to roast until vegetables are tender and deeply caramelized, 20-30 minutes more. Remove from oven and cover loosely with foil.Increase oven temperature to highest setting. Place a baking sheet in oven for 5 minutes. Place cod fillets on hot baking sheet and cook until juices from fish turn from clear to opaque, 10-20 minutes depending on thickness of fillets. Remove from oven and transfer fillets to a large platter and keep warm.
Remove foil and reheat vegetables in oven until very hot, about 5 minutes. To serve, place vegetables around fish and sprinkle with 1/2 teaspoon fennel pollen (optional). Garnish with 1/2 cup chopped mixture of fennel fronds, parsley and chives.