Ingredients
2 - 3 tablespoons olive oil
3 diced onions
1/2 teaspoon salt
1/2 cup plain thick yogurt (Greek is best!)
1 cup sour cream
3/4 cup mayonnaise
1/4 teaspoon garlic powder or fine minced garlic
dash black pepper
chopped green onions for garnish (optional)
Steps

1. Sauté onions in a skillet over medium to low heat until they are golden brown, but not burned.  Stir fairly frequently to keep from scorching.  Stir in salt the last few minutes.  Set aside to cool when done.
2. Add yogurt, sour cream, mayo, and seasonings to a bowl and stir.  Then put in the onions and give it another stir or two.  Add salt and pepper to taste.  
3. Chill in fridge for about 2 hours or overnight, covered.  Garnish with chopped green onion (optional) before serving.​