1 tablespoon olive oil
4 tablespoons unsalted butter
1 teaspoon salt
1/2 teaspoon freshly ground black pepper
1/4 teaspoon ground cayenne pepper
1 teaspoon sugar
1/2 cup mayonnaise
1/2 cup sour cream
4 ounces cream cheese, at room temperature
Cut and slice the onions into 1/8-inch thick half-rounds. (You end up with about 3 cups.) Heat oil and butter in a saute pan over medium heat. Add onion slices, all the seasonings, and sugar. Saute for 10 minutes until the onions have begun to soften. Reduce to medium-low heat and cook, for 15-20 minutes (stirring occasionally) until the onions are browned and caramelized. Remove from heat and let cool. Place the remaining 3 ingredients in the bowl of an electric mixer fitted with the paddle attachment and beat until smooth. Add the onions and mix well.