Charred Brussel Sprouts can be made with no oil if you know how to sauté with dry heat. These are not covered in butter and oils which makes them incredibly low in calories.
To make the cooking process quicker, place brussel sprout quarters into a microwave bowl and cook for 3 minutes on high.
Heat a medium sauté pan. No oil is needed as you will be using a "dry heat" method to sauté the brussel sprouts. The pan is ready when a drop of water dances in the pan like a ball of mercury.
Add brussel sprouts and chopped onion. Allow to brown on one side then toss to brown on the other sides.