Heat the oven to 420 degrees Fahrenheit.
In a baking dish, put all the ingredients except the salt. Cover with aluminum foil and place it in the oven.
Cook for an hour and a half covered. Uncover, add salt, and mash the tomatoes down with a fork.
Cook uncovered till there is almost no liquid left, about 40 minutes. Transfer to a container.
You can get rid of excess oil at the end of cooking.