I'm trying to find a reliable way to make a good base gravy for British Indian Restaurant (BIR) curry -- for those that don't know, this is essentially the adapted form of Indian curry cooking used in Indian takeaways in the Western world (I know, glamorous!).  Base gravy is essentially some alliums and sometimes tomatos / carrot / celery cooked for a long time and then blended to a soup-like consistency (after this, spices and other flavorings are added to achieved a finished dish). The basic sauce of the curry world, essentially.  The key determinant of success seems to be sweetening the onions. I can carmelize them using the standard technique (frying and deglazing), but I'd ideally like something that only uses boiling because it is less work (also, adding a lot of oil to base gravy and then again in the finished dish - to temper the spices - seems unhealthy to me).   And even in the more varied base gravy recipes in which carrots/cabbage/tomatoes have been involved, these ingredients have only been introduced towards the end of the cooking process after a base of well-sweetened onions has already been achieved.  TL;DR Can brown / sweet / onions that don't taste raw be achieved without frying?  Even if you start with frying, can the sweetening process continue to take place while the onions are boiling (once cooking temperatures are below what would be required for the Maillard reaction to take place)?  And if so, how long would the onions need to be boiled to achieve reliable results?  I notice that some base gravy recipes call for boiling the onions for very long periods of time (2 hours) but I didn't achieve what I expected using a slow cooker.  (I feel a little stupid even asking this, but take solace in the fact that learning to produce tasty, consistent base gravy is apparently something that it takes every Indian chef a while to master.) 
Cook's Illustrated recently published a recipe for caramelized onions that took only 20 minutes. The key points:   Cook them in some rapidly boiling water to break down the cell walls, about 15 minutes. After they are fully cooked, add a small amount of baking soda (about 1/4 tsp to three pounds of onions).    The slightly basic solution aids the quick conversion of starches to sugars, and aids browning. In five minutes, you cook off the excess water, as well as rapidly browning the onions without turning them crispy.   The small amount of baking soda suffices to change the reaction rate, without substantially altering the taste. The result is a big pile of sweet, brown caramelized onions; they can be turned into French Onion Soup simply by adding some stock.  Cook's Illustrated recommends slicing pole-to-pole (Lyonnaise) rather than across for this preparation. Apparently it makes them firmer; otherwise, they risk collapsing entirely.  Give this experiment a try, and you may be able to adapt the technique. I don't know if it would adapt well to smaller quantities, but you could cook three pounds and set the rest aside for many, many other uses. (Top goat cheese; put it on a pizza; add to green beans; save for another curry.) 