There are several ways to saute onions – resulting in different degrees of caramelization.
The first is to fry the onion in oil and/or margarine till translucent, over medium-low heat. The onion still has firmness and is essentially a stir-fried onion, like the Chinese do.
I often say in a recipe to fry till translucent, then add the other ingredients that take a shorter amount of time to cook, so that when all is done, the onion is perfect.
If you go a step further, the onion is translucent and brown-tinged around the edges, and cooked over medium heat. This is when you want a small char taste to the onions that will be imparted into the final dish.
Still further, whereby there’s a tan-colored look to most of the onion with a little char and they’re moderately soft to the tooth, but not mushy, you now have a light caramelized onion, that can be served as a side dish or as a topper for veggie hot dogs, subs or veggie burgers. This is also done over medium heat.
When you’re reaching for a dark caramelization, you cook the onion over low heat for a long time. There’s no char, but the onions are very soft, but not mushy, and equally brown-colored.
TRANSLUCENT AND BROWN-TINGED
LIGHT CARAMELIZATION WITH SOME CHAR
DARK CARAMELIZED ONION