Rich and savory with a hint of sweetness and herbal rosemary, this jam would make an excellent side dish on your holiday table. Served with biscuits or toast, spread on your turkey, or swirled in your mashed potatoes, it's a versatile condiment that's packed with flavor.
- Preheat oil in a large skillet over medium heat. Add onions. Cook, stirring occasionally, until onions are soft, translucent, and just beginning to brown, about 20 minutes.
- Stir in balsamic vinegar, brown sugar, rosemary, and salt and pepper. Continue to cook, stirring occasionally, until liquid is evaporated and onions are dark brown and reduced to 3/4 cup, about 40 minutes more.
- Remove from heat and let cool. Store in a glass jar or airtight container in the refrigerator for up to 1 week.