1 T unsalted butter
1 T vegetable oil
3 red onions (about 1-1/2 pounds), sliced into 1/4-inch thick half moons
1/2 C dry red vermouth or wine
1/4 C firmly packed light brown sugar
1/2 t salt
1/4 black pepper
1/4 C balsamic vinegar
1 T chopped fresh rosemary (or 1-1/2 t dried)
1 T chopped fresh thyme (or 1-1/2 t dried)
In a medium, heavy bottomed nonreactive saucepan, heat butter and oil over medium heat. Add onions and cover. Cook, stirring occasionally, until softened, about 5 minutes. Add vermouth, brown sugar, salt, and pepper and bring to a boil. (if using dried herbs, add them now, too). Simmer until onions are tender, about 40 minutes.
Add vinegar and fresh herbs. Increase heat to high and cook, uncovered, stirring often until liquid is reduced to a glaze, 3-5 minutes. Serve at room temperature.