To caramelize onions, simply add about a tablespoon of olive oil to a pan, add thinly sliced onion and cook them down over medium-high heat, stirring frequently until the onions are very soft and turn a deep golden color. If they begin to burn to stick to the pan, add a little bit of stock of your choice, water or wine to the pan and continue to cook until the onions are ready and the liquid is completely evaporated.