1. In a nonreactive stock pot heat the butter. Cook the onions over low heat until very soft, about 40 minutes. Add the sugar and continue cooking until the onions caramelize and are golden brown, about 10-15 minutes.
2. Add the remaining ingredients and simmer partly covered for 20 to 25 minutes. Most of the liquid should be absorbed and the mixture will have the consistency of jam. Serve warm or room temp.