In a large skillet, over medium heat, heat the olive oil.
1 tablespoon olive oil
Add in the finely diced onions and water. Cook for 5-7 minutes until the onions have softened. Set the onions aside.
1 medium yellow onion, 1 tablespoon water
Place your hamburger buns onto a sheet pan, with the cut side up, and spray them with nonstick cooking spray. Place under the broiler in the oven until golden brown.
4 hamburger buns
Evenly divide the sautéed onions onto the bottom buns. Spread about 2 tablespoons of the butter onto each top bun. Set them aside.
1/2 cup (1 stick) salted butter
Divide the ground beef into four equal sections (or do six equal sections for thinner burgers, this is what I do) and shape them into balls.
1 pound ground beef
Preheat your griddle, or outdoor grill, to medium-high heat.
Place the ground beef balls onto the griddle. Using a spatula or burger press, flatten them into thin patties. Season the patties with salt and pepper. Cook for 3-5 minutes and flip the patties over. Top each burger patty with a slice of cheese and continue cooking for about 3-5 minutes, or until the patties reach your preferred internal temperature for doneness. See notes below.
kosher salt & ground black pepper, 4 slices American cheese
Transfer the burger patties to the bottom buns and top them with the buttered top buns. Serve immediately and enjoy with your favorite hamburger toppings!