The simple answer is: it obviously all depends on the quality of the tomatoes! However, as with all cooking, your own tastes play a pivotal role, too.
Essentially, the less ripe your tomatoes, the more likely they’ll be to need a little something to help them along. Not only that, since plenty of tomatoes are really quite acidic, they will only benefit from a bit of added sugar.
Some opt for a teaspoon of sugar, or to taste, for every kilo of fresh tomatoes (or 800g of tinned), whereas others add the same amount to sugo made with tinned, but omit it when good fresh tomatoes are on the market. My mother adds just a little sugar to her sugo by default, and my father only if needed.
I believe it’s all about the tomatoes. Good ones will be sweet enough as they are. That said, officially the best sugo recipe in the whole world ever (don’t all @ me at once, please: it’s just a statement of fact), namely “tomato sauce III” in Marcella Hazan’s 1976 Classic Italian Cookbook, includes a quarter-teaspoon of granulated sugar per kilo of ripe plum tomatoes.
To make it…
- Wash and halve the tomatoes, then simmer in a covered pot for 10 minutes.
- Pass the now slightly slumped fruit through a food mill back into the pot, add 110g butter, a peeled and halved onion, a touch of salt and the sugar, and leave to burble and reduce gently, lid off, for 45 minutes.
- Pick out the onion, adjust the sauce for salt, then toss through cooked pasta or gnocchi.
- You’ll never view pasta al pomodoro the same again, promise – as Hazan so modestly put it, this sauce is “unsurpassed”, and who am I to disagree?