1) Add butter to a medium pan over medium heat along with sliced white onions. Sprinkle with a pinch of salt and let the onions cook, stirring occasionally, until they are cooked down and a light brown color, about 15 minutes. You can work on the other parts of the sandwiches while you cook these down.
2) Divide the ground beef into four even-sized patties that are roughly the shape of your bread slices. It’s okay if they are on the thin side. Season each patty with salt and pepper.
3) In a large skillet or on a griddle over medium-high heat, add the patties and cook until they are cooked through, about 3-4 minutes per side.
4) Remove the patties from the heat and add a drizzle of oil to the pan or griddle. Place the bread slices down on on the pan and spread a liberal amount of hummus on each piece. Turn heat down to medium so the bread doesn’t burn.
5) Top the hummus with a patty per piece of bread. Divide the onions between the patties and top each with a slice of cheese.
6) Top each sandwich with the other piece of bread. I like to drizzle a little extra oil over the top of the sandwiches.
7) Let the sandwiches cook for 3-4 minutes on the first side and then flip each sandwich. Cook on the second side for a few minutes. If the bread is burning or the cheese isn’t melting, you can add a spoonful of water to the pan and cover the sandwiches with a bowl. The steam will immediately melt the cheese and make the patty melt really cheesy and delicious. You might not need to do that though.
8) Take the sandwiches off the heat when the cheese is melted and the bread is golden brown. Slice them in half and serve immediately!