You bought the same brand of "domestic" San Marzano tomatoes as I did. I hope yours are better than the ones I got.
I also have a Rao tomato sauce, a puttanesca sauce. As native New Yorkers know, Rao's is a famous New York City Italian restaurant that is almost impossible to get reservations for. From what I can tell, it is reserved almost exclusively for regulars or guests of such regulars and by invitation only. For those who can't get into the restaurant, they can buy the Rao line of (expensive) sauces that are sold by many specialty food stores around the country (and from Rao's website). The jar of Rao sauce I have lists imported Italian tomatoes as the main ingredient for the sauce, but elsewhere on the label it says that the sauce is "made with imported Italian tomatoes from the San Marzano region." I suspect they are not of the D.O.P. type, but rather other tomatoes grown around Naples.
The use of meat-based ingredients in tomato sauces is quite common, most usually among Italians, who quite frequently refer to their tomato sauces as "gravy". More often than not, the sauces are for use on pasta, as is the case with Rao's sauce using fatback or salt pork. Wolfgang Puck's favorite tomato sauce (or so he says) uses chicken stock. However, there is a well known pizzeria in Naples, called Porto Alba Pizzaria, that uses fatback or salt pork and beef stock for a tomato sauce for use on pizzas. I will try to find the recipe and post it later today.
If you are interested in a basic Rao marinara sauce, here is what is reputed to be Rao's actual recipe as used in his restaurant:
4 (28-oz.) cans imported Italian plum tomatoes with basil, preferably San Marzano tomatoes
1/2 c. extra virgin olive oil
4 oz. fatback or salt pork, optional
6 T. minced onion
4 garlic cloves, peeled and minced
Salt, to taste
12 leaves fresh basil torn, optional
Pinch dried oregano
Pepper, to taste
Remove the tomatoes from the cans, reserving the juice in which they are packed. Using your hands, crush the tomatoes, and gently remove and discard the hard core from the stem end and any skin or tough membrane. Set aside.
Put the olive oil in a large, nonreactive saucepan over medium-low heat. If using fatback, cut it into small pieces and add to the pan. Sauté for about 5 minutes or until all the fat has been rendered. Remove and discard the fatback. Add the minced onion and sauté for 3 minutes or until translucent and just beginning to brown. Stir in the garlic and sauté for 30 seconds or until just softened. Stir in the tomatoes, the reserved juice, and salt. Raise the heat, and bring the sauce to a boil. Immediately reduce the heat to a very low simmer and cook the sauce for about 1 hour or until the flavors have combined and the sauce is slightly thickened. If you prefer a thicker sauce, cook for an additional 15 minutes. Stir in the basil, oregano, and pepper, and cook for an additional minute. Remove from the heat and set aside or refrigerate until ready to use.