For any cut of onion, start by cutting off the stem end and root end of the onion. Turn the onion cut sides up and down, and cut the onion in half. Peel the onion and remove any tougher outer layers.
1
Heat butter or oil in a large cast iron skillet over medium low heat. Add onions in batches. As onions wilt down, add more onions until all onions can fit in the pan.
Add salt to taste. Start off with less than you think you will need. The onions will shrink down a lot, and you can always add more salt later.
3
Keep stirring the onions every few minutes, scraping up any fond. Onions will go from white/yellow, to golden, to golden brown, to dark rich brown as they caramelize.
After about 30 minutes of stirring and scraping, onions should be almost dark brown. Add a few tablespoons of your deglazing liquid to the pan & use it to scrape up the fond from the pan.
They are good in just about everything! Add to burgers, sandwiches, steaks, chicken, charcuterie boards, hotdogs or brats, patty melts, or even this Baked Brie with Fig Jam & Caramelized Onions.