INGREDIENTS
1 tablespoon extra-virgin olive oil
4 cups onions, chopped
3/4 teaspoon salt
1 can (14-ounce) reduced-sodium beef broth, or 1 3/4 cups mushroom broth
2 teaspoons onion powder
2 tablespoons distilled white vinegar
1 cup reduced-fat sour cream
1/3 cup nonfat plain yogurt
DIRECTIONS
Heat oil in a large skillet over medium-high heat. Add onions and salt; cook, stirring occasionally, until beginning to brown, 6 to 10 minutes. Add broth, scrape up any browned bits, and simmer until liquid is almost evaporated, 10 to 20 minutes. Reduce heat to medium-low and cook until onions are deep golden brown, 5 to 8 minutes more. Stir in onion powder, then stir in vinegar and cook until evaporated, 1 to 2 minutes. Remove from heat and let cool for 20 minutes.
Combine sour cream and yogurt in a medium bowl. Stir in onion mixture. Chill for at least 30 minutes to blend flavors.