Not a stuffed onion, but a really easy and good baked onion, and as usual for me, not really a recipe:

Peel as many Vidalia onions as you need servings, leaving them whole. Make a small hole in the center of each, leaving most of the onion. Stuff a beef bullion cube and as much butter as you can into the hole. Season with salt and pepper, and maybe some thyme (fresh or dried will work fine.) Wrap in foil and place on a baking sheet. Bake at 350 for 30 minutes to an hour, depending on how soft you like your onion.

This makes a great side dish.