Kenji came up with a method[0] which actually only takes ~15 minutes -- but it does produce very mushy onions, so it won't work for all applications.
0. https://www.seriouseats.com/quick-caramelized-onions-recipe
0. https://www.seriouseats.com/quick-caramelized-onions-recipe
[0]: https://news.ycombinator.com/item?id=36038796