hello Pizza De Puta,
let me start by saying that Mark is correct. I was told by many Pizzeria owners to never blend your San Marzano Tomatoes, but to only smash them down with a potato masher. The reason is that the seeds that are chopped up by a blender or food processor can make the sauce have a bitter taste. Also, I too, have found that most Pizzerias do not add anything to the crushed San Marzano Tomates other than to sprinkle some sea salt over the crushed tomatoes after they are spread around the pizza dough.