You can also make your own from fresh tomatoes of course. Roma or other dense varieties. Very low heat and stir till your arm falls off, then stir some more. Go easy on the herbs.
Or use a handheld electric mixer, which I've seen my wife do.
When she does lasagna sauce, at one stage she will transfer the sauce to a food processor, blend it for a while, then put it back in the pot.
There's also this method: