I used the left-overs from my roasted chicken with potatoes and onions the night before. If you want to make it without left-overs, just roast quartered potatoes and onions at 400 degrees for 1 hour.
4 roasted potatoes, diced
1 roasted Mayan onion, quartered
1/4 cup red wine vinegar
1/4 cup olive oil
2 green onions, diced
1/2 Tbsp. brown sugar
Salt and Pepper to taste
Put the roasted onion in a food processor, along with the vinegar, olive oil, and brown sugar. Process until smooth. Pour over diced potatoes and green onions. Add salt and pepper. Chill at least 1 hour.