Omelette à la Lyonnaise from Richard Olney's book “Simple French Food”. I had a bunch of onions that were about to go bad and voilà this was the perfect solution. Onions are reduced in butter for 30 minutes, then added to 3 beaten eggs and cooked as on omelete. When done, pour some brown butter on top of the omelete. To that brown buttered pan add one tablespoon of wine vinegar, swirl it for the vinegar to meet the leftover butter brown bits and pour that on top of the omelete.