Y helo thar. This is a recipe for relatively simple marinara sauce and I think you may like it.
You will need:
One 28-ounce (780g) can of crushed tomatoes
One 14-ounce (390g) can of tomato paste
One eight-ounce (220g) can sliced black olives
One green bell pepper, minced coarsely
One red bell pepper, minced coarsely
One very large onion, minced finely
About a pound (half a kilo) of white button mushrooms, sliced thinly
4 tablespoons food service bulk packed "spaghetti sauce seasoning" (seems to be mostly basil and dehydrated onion flakes)
4 tablespoons chopped fresh garlic, from bulk pack jar
Dash crushed red pepper flakes
Salt to taste (this varies a lot, of course, maybe start at around a tablespoon)
A bit of olive oil
Perhaps a bit of water
Heat the olive oil in the bottom of the pan. Put in the chopped onion and cook it until it begins to caramelize. Add the peppers and mushrooms, and the canned olive slices, including the canning liquid. As the vegetable mass cooks, you may see liquid begin to accumulate in the bottom of the pan. Add the dried spices and stir in, perhaps with a bit of water, so that the spices can absorb liquid and contribute their flavors to the broth. Bring it to a boil, and simmer this mixture a while, watching closely and stirring frequently to keep it from boiling dry and burning.
Stir in the canned tomato paste first and mix more or less completely, then the crushed tomatoes, and bring back to a boil then a very low simmer. Old restaurant cook's trick for simmering tomato sauces without scorching them: put the sauce in a big wide baking pan and put it in a warm oven, around 250 F. (120 C.). The sauce really needs to simmer a while, at least an hour, perhaps even an afternoon. Don't let it scorch.
This makes around eight servings.
It's very good with spaghetti, of course, I find that hot Italian sausage links roasted slowly in the oven, then drained, sliced, and folded in are an excellent complement. Or you could make meatballs of ground beef, minced onion, breadcrumbs, and beaten egg, brown them quickly under the broiler, then drain them, add them to the sauce, and let them finish cooking in the sauce. Or both.