Caramelized Onion Dip

This is a great dip. I don't really care for the pre-made onion dips and decided that making a homemade version was in order. I searched around for ideas and saw one that used caramelized onions. However, after searching my bookmarks, I can't find the site where I found the recipe! Grr... I hate when that happens. So this recipe is my interpretation for the lost original. This is really easy, but be sure to allow enough time for the onions to cool! I brought this to the a Badger Rose Bowl party *tear*. Enjoy!
Ingredients
14 oz plain greek yogurt
1 cup lite sour cream
2 Tlb onion powder
1/2 tsp garlic powder
2 large yellow onions, thinly sliced
2 tsp butter
1 Tbl olive oil

Instructions
Heat butter and oil in a large pan over medium heat. Add onions and cook till they are a rich caramel color. This will take about 20-30 minutes. Becareful not to burn them! Remove onions from pan and allow them to cool to room temperature. In a medium bowl, greek yogurt, sour cream, onion powder, and garlic powder. Add 2/3 of the onions to the yogurt mixture. Mix well. Spread dip evenly in a serving dish and top with remaining onions. Refrigerate till you are ready to serve the dip.