In a medium bowl, combine the 4 ounces cream cheese, at room temperature, ½ cup sour cream, ½ cup mayonnaise, 1 teaspoon kosher salt, ½ teaspoon freshly ground black pepper, ¼ teaspoon cayenne pepper.
Use the hand mixer to beat the ingredients together until smooth (start with slow speed and move up to high, beating for about 1-2 minutes.
Fold in 1 cup caramelized onions until well combined. Taste for seasonings and adjust as necessary.
Transfer to an airtight container (or a bowl covered with cellophane) and refrigerate for several hours for the flavors to marry and thicken slightly.
Serve with potato chips, crudite, or crackers.
Notes
Chopping the caramelized onions before adding it to the sour cream mixture will make the dip easier to scoop.Makes about 3 cups of dip.