Serves 4 to 6.

4 tbsp. butter
2 lbs. onions, thinly sliced
1 1/2 c. (1/2 bottle, or 375 ml.) med.-bodied dry red wine
1/2 c. sherry wine vinegar or wine vinegar
1/4 tsp. salt, or to taste
2 tbsp. honey

Heat butter in a deep skillet. Add onions and cook over low heat, very slowly, until soft and golden; it should take about 45 minutes to one hour. Stir onions occasionally, especially toward the end. Add wine, vinegar and salt; cook over medium heat until liquid evaporates. Add honey and cook slowly until mixture begins to caramelize, about 15 minutes. Taste for seasoning. Serve warm or at room temperature.