You can’t burn them if you do them low and slow. I do mine more-or-less like this, usually with a little sugar and balsamic at the end (onion marmalade, effectively). If you’re doing it too fast, you not really caramelizing them, IMO, just browning them. They don’t turn out properly jammy that way - the sugars are all caramelized at the surface, not inside the cells of the onion. Others haveeven strongeropinions about that.
Quadgop’s method sounds good, too.