Cut the onions in half, and
then slice them into 1/8-inch thick half-rounds.
(You will have about 3 cups of onions) Heat
the butter and oil in a large sauté
pan on medium heat. Add the onions, cayenne,
salt and pepper and sauté for 10 minutes.
Reduce heat to medium-low and cook, stirring
occasionally, for 20 more minutes, until the
onions are browned and caramelized. Allow
the onions to cool.
Place the cream cheese, sour cream, and
mayonnaise in the bowl of an electric mixer
fitted with a paddle attachment and beat
until smooth. Add the onions and mix well.
Taste for seasonings.
Serve at room temperature.