Remove peel and thinly slice onions, about ¼ inch thick.
Add olive oil or butter (or both) to a large skillet over medium heat.
Add the sliced onions and salt and using a wood spoon or heat proof spatula stir to coat in the butter/oil.
Add salt and sugar (if using)
Cook for an 45 minutes to an hour, stirring every 5-10 minutes.
If you need to deglaze, add a few tablespoons of liquid and scrape the bottom of the pan with a wooden spoon or spatula
Cook to desired caramelization and then use in favorite recipe or as a delicious topping for pizza, sandwiches, and more!
Notes
You can use any type of onion you want for this recipe.
The larger the pan you use, the more the onions can spread out and the shorter the cooking time.
When deglazing, a good guideline is about 1/4-1/2 cup total liquid, added 1-2 tbsp at a time. But, there are no hard and fast rules. You can even save deglazing until the very end. Just make sure to keep a close eye on the onions so they don't burn.
The onions really cook down - to about 1/2 cup per large onion depending on how much you caramelize them.
You can easily double or triple the recipe as needed.
These will last 3-5 days in the fridge or can can be frozen up to 2 months.