1. In a large pot, heat the oil over moderately low heat. Add the onion and garlic and cook, stirring occasionally, until the onion is translucent, about 5 minutes. Stir in the tomato paste, cumin, red-pepper flakes, black pepper, and 1/2 teaspoon of the salt. Cook, stirring, for 2 minutes.
2. Add the broth and bring to a simmer. Add the potatoes and carrots and simmer for 10 minutes. Stir in the turnip, zucchini, and the remaining 1/2 teaspoon salt. Simmer for 10 minutes longer. Add the cod, bring back to a simmer, and cook until just done, about 3 minutes. Serve the stew topped with the parsley.
Fish Alternatives: Any relatively firm, white-fleshed fish will work well. Try rockfish, grouper, or for a special treat, halibut. Be sure to remove the skin before adding the fish to the pot.
Wine Recommendation: Serve a cold glass of rosé with this Mediterranean-inspired dish. Try Côtes de Provence or Bandol, both from France, or one of the new drier rosés from California.