How to Caramelize Onions

1 Slice the onion into very thin rounds using a sharp knife or a mandoline slicer.
2 Melt the butter in a nonstick skillet over medium heat. I like to use a light-bottomed pan when I can to keep an eye on the caramelization process.
3 When the butter is bubbling, add the onion and season with a healthy pinch of salt. This will encourage the onions to release their juices, which will speed up the process.
4 Move the onion around the pan with a wooden spoon, cooking it down until it turns into a light brown color. It will become jammy and sticky. (This will take between 30-40 minutes, just depending on your stovetop and how high of a heat you feel comfortable caramelizing with.) You may lower the heat as the onions begin to caramelize so that they don’t crisp up.
5 Let cool and then use.