Practically every recipe calls for getting onions to do something! Translucent? Soft? Golden? Caramelized? The point of most of these techniques is to extract the natural juices that are trapped in the raw onions' cell walls. By adding heat, these walls break down, releasing sugars and flavors, which add complexity and dimension to food. Simply adding the raw onion to foods will achieve little, since it is the slow stewing in a medium such as oil or butter that draws out those flavorful elements.

After a few minutes of sizzling gently in oil or butter, onions wilt as their cell walls collapse, giving up their juices. This gives the once-opaque raw onion a watery, “translucent” appearance. The edges, once rough and sharp, are then “soft.” As the water evaporates from the juices, the onions' natural sugars concentrate on the exterior of the pieces, and brown in the heat. The first stages of this transformation give onions a golden appearance. Since browned sugar is known as caramel, the browning of onions is often referred to as “caramelizing.”