Form the ground beef into 6-7 large beef patties. Dice the onion into small pieces.
Heat a skillet or large pan to medium-high heat. Place the onions in the pan and let them start to sweat for 1-2 minutes. Place the burger patties into the bed of onions. Let the beef cook for 3-5 minutes on the one side until nice and browned.
Flip the burger patties over to the other side. After 2-3 minutes, begin breaking up the burger patties into large pieces. You want to keep large pieces, don’t turn it into ground beef. This will dry out the meat. Keep large pieces. Turn down the heat and spread the cheese slices over the beef. Let the cheese melt.
Spread the hoagies out on a pan. Spread mayo and bbq sauce over the hoagie buns. Add the beef to each hoagie.
Slice the tomatoes. Shred the lettuce and then top the burgers with these items. Serve warm.