De-salt cod for 24 hours (see above)
Preheat oven at 350 degrees Fahrenheit (180 Celsius).
In a pan sauté the onion until soft for about 10 minutes.
Once the onion is sautéed, add the garlic and sauté for about a minute. Add the tomatoes, the tomato paste, the parsley, the wine, lemon juice and pepper (add 1/2 tsp of fine sea salt if using fresh cod).
Bring the sauce to a boil and then lower the heat and let it simmer for about 10 minutes.
Oil a large pan and place the sliced potatoes on the bottom. They should not overlap. Over that place the pieces of cod (rub the cod with kosher salt if using fresh cod)
Once your sauce has simmered for 10 minutes, add the raisins.
Pour the sauce over the cod and potatoes (remove bay leaf), moving things around so that the sauce has gone everywhere. The sauce will not be very thick.
Cover the pan with aluminum foil and cook covered for about 35 minutes, uncover and check potatoes, they should be fairly easy to pierce. Cook for another 15-20 minutes uncovered, until potatoes are done and all the liquids (except the olive oil) are gone.
Remove from oven and let it sit for 15 minutes before serving.