Ah, the juicy burgers of summer cookouts! They taste so good -- but are so often huge fat and calorie bombs. The sad truth is that most homemade burgers have well over 800 calories. But it is possible to pack all that savory meaty flavor, oozing melting cheese and even bacon into a big, satisfying burger without blowing your dietary allotment for the entire day.
Combine the mayonnaise and ketchup in a small bowl and set aside.
Heat a medium skillet over medium heat; add the bacon and cook, turning once, until crisp, 7 to 8 minutes. Transfer to a plate covered with a paper towel and drain; chop.
Gently combine the beef, garlic powder and 1/4 teaspoon each salt and pepper in a bowl. Divide the mixture into 8 portions and form each into a 3 1/2-inch-diameter patty; put 4 patties on a work surface. Toss the bacon with the cheese and spoon a quarter of the mixture on top of each of the 4 patties, keeping the edges clear. Place the remaining patties over the cheese and pinch the perimeter to seal the filling in.
Grill the patties with the lid closed, turning once, 9 to 10 minutes for medium doneness. To assemble, put the bottom half of each roll on a plate and top with a lettuce leaf, tomato slice and patty. Spoon the mayonnaise mixture over the patties, then top with the onion slices and the remaining roll halves. Serve immediately.