Preheat the oven to 450 degrees F.

In a large, enameled cast-iron casserole with a lid, heat the olive oil. Add the onion and garlic, saute over medium heat until softened, about 8 minutes.

Add the parsley and crushed red pepper and cook over moderate heat, stirring, for 1 minute.

Add the tomatoes and cook until almost all of the liquid has evaporated, about 5 minutes.

Arrange the halibut fillets in the casserole and season with salt and pepper. Scatter the olives over the fish and top with the shrimp. Tuck in the clams and mussels, hinge sides down.

In a medium saucepan, bring the clam juice and white wine to a boil. Pour the hot liquid over the seafood.

Cover the casserole dish, transfer to oven and bake for about 30 minutes, or until the mussels and clams open, the shrimp are pink and the halibut is cooked through. Discard any shellfish that don’t open.

Spoon the broth into serving bowls, top with seafood and serve.