Properly caramelized onions freeze and thaw very well, since they are already pretty broken down and much of the moisture is gone. Since the big factor is the

Properly caramelized onions freeze and thaw very well, since they are already pretty broken down and much of the moisture is gone. Since the big factor is the 40-60 minutes on the stove, I make a large batch in several pans. The onions can be cooled a bit and then individual portions in an old ice cube tray and frozen. Then I can just pop out an onion cube and microwave it until softened, anytime I'd like to add caramelized onions to something.