Cut the cod into 8 to 10 serving pieces. Though you can cook whole filets, it will be easier to get the fish out of the pan if cut into portions.
In rondeau large enough to hold the fish in one layer, sauté the onion and a sprinkling of salt in the olive oil until transparent and slightly golden but not brown.
Add the garlic and sauté until fragrant, about 1 minute.
Add parsley and some freshly ground black pepper. Sauté for a minute or two. The smell of parsley should become noticeably more potent. Do not brown the ingredients of the pan.
Add the wine and cook briskly until the wine evaporates.
Add the tomato paste. Sauté, stirring frequently, until it gets ever so slightly darker and begins to smell sweet. This will take 2-3 minutes.
Add the water, oregano, basil and additional salt and pepper to taste. Boil gently, with the cover slightly askew for 20-30 minutes. The sauce will thicken. If it becomes too thick, add a little additional water. However, the juices from the fish will thin the sauce so it is better for the sauce to start out too thick rather than two thin. The sauce can be made ahead to this point.
With the sauce at a medium boil, add the fish, skin side down. Season with salt and pepper. Cover the pot tightly and cook for approximately 20 minutes until the fish cooks through an flakes easily. The length of time will depend on the type of fish, thickness of the portions, and elevation. Do not turn the fish but occasionally spoon some of the sauce over the top of the cooking fish.
Taste the sauce and adjust seasoning. If the sauce it too thick thin with a little water. If it is too thin, boil it briskly after removing the fish.
Put the fish on a deep serving platter. Pour the sauce over the fish and serve.