This is my Nonni's sauce recipe (more or less.. to taste). It is a super simple Sicilian style sauce without basil or garlic, but you can add those if you want. You can use fresh or organic canned tomatoes, which help cook it faster and bring out the natural sweetness of the tomatoes.
1 large white onion, chopped, sauteed until clear in a bit of olive oil. If you don't use olive oil, I would use an animal lard or butter rather than coconut oil - it would mess with the taste. Add in some oregano now, it helps pull the flavor out.
If using canned, add tomato paste first, cook onions down further with it to caramelize the tomato paste and onions, then add whole peeled canned tomatoes, crushed by hand or chopped up. More oregano (if needed), and only salt and pepper to taste. Let it simmer for about an hour, the longer, the better, especially if you use fresh tomatoes. Roma tomatoes are best because they are low moisture and low seed, which helps them cook down faster and ideal for sauces. One of her tricks to making an "aged" taste is to add Romano cheese (which she also does in her meatballs, which are the best ever, though she puts bread crumbs in hers, I just add one extra egg and they bind just fine because we fry them in olive oil before putting them in the sauce, which helps them brown up and get a nice crust that holds them together). I love Locatelli's Pecorino Romano.. amazing. It makes it sweet, savory and very hearty. Great to add browned ground meat to for a super tasty meat sauce. I make "meat lasagna" all the time, just extra onions for sweetness and texture, browned meat, and the sauce in a casserole dish, baked a bit for additional melding of flavors. Or out of the pot I call it "Italian Chili".