What feature is unique to the Top Shelf Rita?

The option that highlights the unique feature of the Top Shelf Rita is that it includes Cointreau. Cointreau is a high-quality orange liqueur that adds a distinct flavor profile, enhancing the cocktail and differentiating it from other margarita variations. This element contributes to the drink's upscale nature, aligning with its "Top Shelf" designation, which typically indicates the use of premium ingredients.

Including Cointreau not only elevates the drink but also aligns with the expectations of guests seeking a refined experience at Outback Steakhouse. Other choices, such as being the only frozen option or having all organic ingredients, do not accurately characterize the Top Shelf Rita specifically, as the drink can be served on the rocks and may not adhere to organic standards. The sugar rim, while a common feature for margaritas, is not solely associated with the Top Shelf Rita and can be found on other variations as well.