I have never actually made spaghetti sauce at home but we still had a lot of tomatoes and I know the basic idea so ....I winged it.
Then I just simmered it for a couple hours until it looked thick enough. It maybe isn't as thick as store bought but we tried it out and it was pretty good. It only made enough for maybe 3 meals but that is three jars of spaghetti sauce that I don't have to buy and it used up most of the tomatoes.