For the Cheddar fricos: In an 8-inch nonstick pan heated over medium-high heat add 1/4 cup shredded cheese. Cook until cheese is light brown on the bottom. Turn over with a plastic spatula and continue cooking for another 10 to 15 seconds. Remove to a plate to cool. Wipe pan and start again until 6 fricos are complete.
Form 6 (1/2-pound) beef patties and season very well with sea salt and black pepper on each side. Place on a hot grill and cook until nicely browned, approximately 5 minutes. Turn over and continue to cook to desired doneness.
A couple of minutes before the burgers are done halve the rolls and lightly brown on the grill, open side down.
Place burgers on the bottom halves of the rolls, adding a generous helping of onions. Season the tomato slices with salt and pepper. Top the burgers with frico, tomato slice and greens. Roll up your sleeves and dive in.