The first step in carmelization is to remove most of that water so the onions can reach maillard reaction temps. Try doing it without oil and an equivalent amount of water instead. It's much more temperamental.
Where did I say it wasn't?
Anyway, about adding water, I respectfully disagree. The oil is necessary and it really is a tablespoon in a shallow and uncrowded pan with the lid off.
EDIT: I'm specifically talking about browning some onions when called for as an initial step in a recipe, not for making a huge batch of them for use as a condiment. Cutting the onion into finer pieces also speeds things up.
The idea is that adding water, raising it to a boil, and covering the pan reduces the amount of time needed to raise the temperature of the onions to the caramelization point, more than offsetting the amount of time needed to remove the water itself. That plus adding some baking soda near the end reduces the overall time considerably.
Slow cook them first for a few hours at a low temperature and then caramelize after. All your onion in a dry pot. Don't add water. Strain them when done and you have... soggy pale onions. Heat up the biggest pan you have and add some butter to do the caramelization (don't crowd the pan like they do in their video). Add some good balsamic vinegar and brown sugar while you're at it. Be sure to make a huge batch so you can freeze some for later. Don't bag and freeze before letting the onions come to room temperature. It's a lot of water in them onions man, but you can use that strained out water for a vegetable stock!
I don't like them like the Americans do but there is lots of to play with it. (I've even started boiling onions whole before I use them in a bunch of other dishes)
Highly recommend it.