Soak the onions in water for more than 10 minutes, then peel. In a small sauce pan, bring the olive oil and balsamic vinegar to a boil. Add the onions and simmer over medium heat for about 5 minutes.
Once the onions are cooked, add the water and turn the onions over. Cover the onions with aluminum foil that fits right in the pan (otoshi-buta), and simmer over low heat for 15-20 minutes.
I don't season it but if you'd prefer, adjust the taste with salt and pepper.
Put the onions in a boiled and sterilized jar, pour in the juice, and it is done. Once it is cooled, store it in the refrigerator. It tastes better the next day or even the following day.
Serve it with fish or meat dishes. It's perfect for sandwiches, cheese fondue, and raclette cheese.
Italian onion sauce (Recipe ID: 996145)
Story Behind this Recipe
I used to buy stewed onion from a store, but I started making it myself a few years ago. It tastes great with less olive oil as well, so I make it often.
It's convenient if you estimate the amount that can fit in the jar that you are using by placing the onions in before cooking. Take it out from the refrigerator to warm slightly before serving.