We bake them. Here's how.
Peel onions and leave whole. Using a spoon or a melonballer, scoop out a "well" in the root end. Using one onion per person, place the onions into a shallow baking dish, "well" side up. Pour in enough water to 1/4 inch deep in dish. Put one beef bouillon cube in each "well," along with a small slice of butter. Cover with foil and bake in preheated 350F oven for 45 minutes to 1 hour.
These are sooooo good and literally disappear before your eyes. We're addicted to them. They're great with roast beef, pork or chicken.