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:
The one I described is without blenders. The one in the video also used canned tomatoes. You do have to somehow get the skins and seeds out. And I would never put that much basil in anything except maybe pesto. And no pepper—some people don’t like it and others can always add their own.
My grandmother was big on using large chunks of things and then taking them out before serving. She would never have put all that chopped onion and garlic into anything. More like vegetable/tomato soup if you do it that way.
Except for marinara, pieces of fatty pork or something like that were added to give it flavor and then removed.