I love caramelised onions, but I'm too impatient to stand around and wait for it to all happen naturally, the onions softening, the sugars finally coming out and going dark and glassy and delicious.
So, I found a shortcut that I adore~ Thinly slice a red onion, throw it on a screaming hot griddle with a tiny amount of oil (not too much, or it will smoke like crazy) and cook it until it softens a bit and gets a little colour.
Then, splash on a good lug of balsamic vinegar. It doesn't have to be top shelf stuff, but something half decent, and allow the vingear to bubble up and reduce a little.
The sugar in the balsamic will sweeten the onions, the acid will soften them, and they come out beautiful, and have a fantastic smokey-sweet flavour.
If you have cooked some meat to go with, do this process in the same pan, as the vinegar will pick up the meat juices and flavour, and add that to the onions.