Caramelized-Onion Sauce

I served this with a grilled roast rack of pork as I wanted something to complement the smokiness yet not overpower the meat. It was very good, easy to make (I made the whole thing in advance, reheating just before serving), used common ingredients and was well-balanced in flavors. I did add a bit of thickening at the end as it was also served with mashed potatoes and felt it was just a bit too thin. (It didn't really need it though.) Much better than an "ordinary" gravy.