In large bowl, mix pizza sauce and cream cheese until well blended. Stir in pepperoni, onions, bell pepper and 1 cup of the cheese. Cover; refrigerate up to 3 days or.
To make 1 serving, place 2 toasted muffin halves on microwavable plate. Top each half with about 1/4 cup pepperoni mixture and heaping tablespoon remaining cheese. Microwave on High about 1 minute or until hot.