Onion tends to have a sweet and rounded flavor, so that it remains in the background enveloping the other ingredients. The most used varieties in tomato sauces are the white and golden ones, more suitable for long cooking, but even here we do not have a precise rule. To make a good fresh tomato sauce, for example, just let the sliced onion wilt in oil, taking care that it does not brown too much, or become bitter.
The basis of many traditional dishes is soffritto, or the chopped mixture of onion, celery and carrots that acts as a universal flavoring: it is found in Bolognese ragù, in Neapolitan ragù (where the onion is coppery) or in lentil ragù, in a vegetarian version. For those who prefer to give more aroma to dishes, the suggestion is to opt for shallots, which are often also more digestible.
