Serve this with a tri-tip roast

2 T. olive oil
1 thinly sliced red onion
1 thinly sliced large yellow onion
2 bunches green onions, green part only, thinly sliced
3/4 c. balsamic vinegar
1/4 c. packed brown sugar
salt and pepper, to taste

Heat oil in large nonstick skillet over medium heat until hot. Add red, yellow and green onions; cook and stir 8-10 minutes or until onions are tender and beginning to brown. Reduce heat to low; cook 12 minutes or until caramelized, stirring occasionally. Increase heat to medium-high. Stir in vinegar, cook 4 minutes or until reduced by half, stirring occasionally. Stir in sugar, season with salt and pepper as desired. Reduce heat to low, cook 5 minutes more, or until liquid evaporates and onion mixture thickens. Serve on the side with carved roast or other beef.