Cook the beef and onions: place a large pan or griddle over medium high heat. Add a tablespoon of canola or vegetable oil.
Once the oil is shimmering, add diced onions and cook for 2 minutes, stirring occasionally.
After two minutes, add the ground beef to the onions. Season with a good dash of adobo seasoning and cook until the beef has browned, and the onions are soft, about 6 or 7 minutes.
When the beef is fully cooked and browned, add your slices of cheese on top of the beef/onions and allow the cheese to soften for 2 minutes.
Chop the cheese: after the cheese is softened a little, using a spatula, stir the cheese into the beef and onions.
Split your roll and open it up. You can add condiments to the bread now or wait until the end.
Using your spatula, scoop the beef and cheese mixture into your split roll.
Add shredded lettuce and sliced tomato and any ketchup or mayonnaise that you would like.
Serve and enjoy.