What additional ingredient is found in the Burrito Supreme aside from beef and beans?

The Burrito Supreme from Taco Bell is known for its combination of flavors and textures, typically including beef, beans, and other key ingredients that enhance its overall profile. One of the hallmark additions to this burrito is onions, which add a crisp texture and a slightly sharp flavor that complements the savory elements of the beef and beans. Onions are a common ingredient in a variety of Mexican-inspired dishes, and their presence in the Burrito Supreme helps to create a more complex and enjoyable eating experience.

The other ingredients mentioned, while they might be found in other menu items or customizable options, do not specifically belong to the standard composition of the Burrito Supreme. Guacamole, rice, and chipotle sauce are not part of the essential ingredients for this particular burrito, making onions the correct choice as the additional ingredient that consistently appears alongside beef and beans.