The Marinara

The trick to a good marinara is to cook at a medium simmer at least for 45 minutes.
First, there is a difference between a marinara and tomato sauce. The latter you find readily in bottles at your supermarket.
To the point,marinara consist of olive oil, tomatoes, a strong among of garlic, a dried chile or some pepper flakes, and dried oregano or fresh basil.
You are right, to ask, "where is the onions, tomato paste and as one chef once asked me at an Orlando interview in1997, "you don't addd sugar?" I said no! Never got that job.

Marinara Sauce:

1 28oz whole tomatoes or crushed
1/4 cup olive oil
8 garlic cloves, peeled slivered
1 small dried chile or pinch of flakes
1 t kosher salt
1 lg sprig basil or 1/4 t oregano

Crushed tomatoes in lg bowl. with one can water.
Using a large skillet at medium, heat oil and add garlic don't brown
Add tomatoes with all liquid, chile, oregano salt and stir.
Add basil, let it wilt and submerge.
Keep simmering for about 15 minutes.
Taste, remove chile and basil.
Serve mixed with pasta, not on top.
Cheese is optional.