4    Yellow onions (~1.5 lb)
2 tb Butter
2 tb Balsamic vinegar
1 tb Brown sugar

Slice the onions into half rings (looks better than cubes) and cook in
butter over medium heat until they start to caramelize (ie turn brown on
the edges). Then add vinegar and sugar and simmer for 10 minutes. Ive made
it with honey, but I think the brown sugar produces a better flavor.