Form the ground sirloin into 4 (8-ounce) patties. Over an open-flame, grill each burger to desired temperature. While the patties are grilling, cook bacon in a skillet until desired crispness, and set aside. In the same skillet that you cooked the bacon in, fry the eggs until set. Transfer to a plate and top each with a slice of cheese.
Butter both sides of each bun and grill until toasted. On each of the 4 bottom buns, place the burger, followed by the cheese-topped egg and bacon, in that order. On each of the top 4 buns, place the lettuce, tomato and red onion, in that order. Top with any additional condiments desired, sandwich the 2 sides, and serve.