First of all, to prepare the sweet and sour sauce, chop the onion.
Then take a saucepan where we will brown the onion and add the rest of the ingredients which will have to boil over moderate heat for about 5 minutes.
The sweet and sour sauce can also be prepared with tomatoes, by changing the doses of the ingredients and mixing 2 tablespoons of concentrated tomato sauce, sugar, vinegar, soy, 1 tablespoon of sake and finally 1 tablespoon of cornstarch.
This sauce is used to season many types of dishes such as fish, fried fish, the sauce with the addition of tomato is instead used to season boiled beef and sweet and sour pork.