- 3 tablespoons butter
- 3 red onions, thinly sliced
- 1 bay leaf
- 1/4 cup brown sugar
- Salt and pepper, to taste
- Pinch of red pepper flakes (optional)
- 3/4 cup dry red wine
- 2 tablespoons red wine vinegar (optional)
Melt butter in a heavy saucepan over medium-low heat. Stir in onions and bay leaf. Cook, stirring occasionally, until onions are soft and lightly caramelized, about 30 minutes. Stir in sugar, salt, pepper and red pepper flakes; continue cooking for an additional 10 minutes.
Add wine and vinegar and simmer, uncovered, stirring occasionally, until liquid thickens and becomes syrupy, 30 to 45 minutes. Remove bay leaf and cool jam to room temperature. Store in a clean jar in the refrigerator for up to 2 weeks.