Food - Drink
Why Adding Salt Is So Important When Cooking Onions
Multiple recipes for cooking onions involve chopping or dicing, and then sweating in some fat such as olive oil before proceeding with the next steps. This creates a base of soft, flavorful onions that meshes easily with other ingredients — and you may have noticed that "sweating" an onion involves adding salt to it.
The cooking technique of sweating an onion refers to cooking onion in some fat over low or medium heat, causing it to soften and release some of its moisture. A common step in soups and stews before adding other ingredients, sweating an onion almost always involves adding some salt to it as it's cooking.
Per The Splendid Table, adding salt to onions immediately after placing them in a hot pan to sauté draws the moisture out of the onions through osmosis. While the liquid is released, the onions will cook a bit faster, have a softer texture that will combine well with the other ingredients in your recipe, and give the onions more flavor.