I may also occasionally fry up a skillet of them with some mushrooms and eat it as a meal. Or I may not, who can say.
Cut onions into 1/2" slices. Remember that they will shrink somewhat significantly, so it's always better to toss an extra onion in the pan. Above I was using 2 medium sized yellow onions. Pour enough fruit juice into the pan that they're almost covered. I use whatever juice I have around: apple, orange, pineapple, it doesn't matter. Sprinkle about a tablespoon of sugar, a teaspoon of salt, and a dash of fresh ground black pepper.
Cook the onions over medium high heat until the juice begins to bubble, then reduce heat to low. Cover and simmer until the liquid has completely evaporated, stirring occasionally.
This is what they look like when they're done. Of course, if you like yours to have a nice blackened, crispy edge, throw a tablespoon of butter in the skillet and bring the pan back up to high for just a minute or two. Watch closely, as they can be easy to burn that way. I find them tasty enough just like this.
Also since most of the sweetness is derived from the natural sugars in the fruit juice, they don't have much in the way of fatty calories. Granted this depends largely on what you use. Cranberry juice cocktail is going to pack a more caloric punch than a can of 100% pineapple juice (my preference).
I'm going to put a recipe up here later this week that will use these bad boys. Maybe you can find a use for them in the mean time?