For the Lime Mayonnaise, mix mayonnaise, lime juice and 1 teaspoon of the Marinade Mix in small bowl until well blended. Cover. Refrigerate until ready to serve.
For the Stuffed Avocado, halve and seed avocados. Carefully remove peel, leaving each half intact. Lightly season with salt and pepper. Mix cheese and tomato. Set aside.
For the Burgers, mix ground beef and remaining Marinade Mix until well blended. Shape into 4 patties. Grill over medium heat 4 to 6 minutes per side or until burgers are cooked through (internal temperature of 160°F). Grill avocado halves, cut-sides down, 30 seconds. Turn over avocados. Place 2 tablespoons of cheese mixture into each avocado half. Drizzle with hot sauce, if desired. Grill 4 to 5 minutes. Toast rolls on the grill, open-side down, about 30 seconds.
Serve burgers on rolls topped with stuffed avocados and onion slices. Press roll gently to smash the stuffed avocado. Serve with Lime Mayonnaise.