Vinaigrette: Roasted Onion Vinaigrette

1 medium sized red onion
? cup olive oil, plus more for drizzling
? cup balsamic vinegar, plus more for drizzling
1 tablespoon lemon juice
1 teaspoon brown sugar
? teaspoon freshly ground pepper
1/8 teaspoon salt
1-2 tablespoons water, optional

Heat oven to 400. Place onion on a large sheet of aluminum foil and drizzle with oil and vinegar. Roast 45-60 minutes, until soft. Peel and process in food processor with other ingredients, except water, until it is smooth. Think with water to desired consistency.
from 50 Best Salad Dressings.