Alton Brown's Onion Dip from Scratch

2 tablespoons olive oil
1 1/2 cups diced onions
1/4 teaspoon kosher salt
1 1/2 cups sour cream
3/4 cup mayonnaise
1/4 teaspoon garlic powder
1/4 teaspoon ground white pepper
1/2 teaspoon kosher salt

In a saute pan over medium heat add oil, heat and add onions and salt. Cook the onions until they are caramelized, about 20 minutes. Remove from heat and set aside to cool. Mix the rest of the ingredients, and then add the cooled onions. Refrigerate and stir again before serving.