With one rule: Never, ever, under any circumstances add sugar to sauce. No ‘just a pinch’ no nonsense about your immigrant grandmother, just don’t do it. Now that you know the one rule let me give you the history behind the sugared sauces.
If you have ever bought a jarred tomato sauce and read the ingredients they usually include Sugar, High Fructose Corn Syrup, Fructose, evaporated cane juice (sugar) evaporated pear juice (also sugar) as well as unhealthy oils like Canola.
In the US the biggest wave of italian immigrants came between 1880 and 1914. Tomatoes were available but the Roma grown in volcanic soil was not. Many of the varieties were more acidic. They were not available year round.
Enter the canned tomato, both home canners and commercial canners used a lot of citric acid to preserve the tomatoes, thus giving them more acid, and a sour taste. It was quite natural for an immigrant who tasted something sour to add sugar to sweeten it,and many of the immigrants were from Southern Italy and did just that.
Those that came from Northern Italy in the area in and around Bologna would often try to replicate the Bolognese sauce and used finely diced carrot which is naturally sweet and no sugar.
Modern canned tomatoes do not have high levels of citric acid and modern fresh tomatoes have been bred to be sweeter so if you live in 2020 and are still adding sugar, you are just doing it out of habit. Sugar does not neutralize acidity it just makes your sauce taste like ketchup.
So how can you make a simple sauce for one or 20?
For each portion:
One small onion
Two clove garlic
Dried or fresh herbs
Two Roma tomato or equal amount of another fresh tomato or 1/2 cup of sauce or canned tomatoes.
Warm a little olive oil in the pan, add the chopped onion, when it begins to soften the chopped or slice garlic and any dried herbs you choose (if using an ‘Italian’ blend keep in mind that it probably contains Rosemary and Oregano so use lightly.
When the house begins to smell like heaven add the tomato. If chopped let cook for a bit and then mash with a fork. Throw in a little water and simmer for 30 minutes or so. Salt to taste, a little pepper and you are good to go.
Cook the pasta according to lesson 1 (https://never-trust-a-skinny-chef.com/2020/03/25/how-to-boil-water/)
And eat a wonderful simple meal. Garnish with cheese, bread crumbs, fresh basil or chives, or chopped olives.
And if the sauce is not sweet enough for you to go Jollibee in the Philippines, they put ketchup on spaghetti.