Heat a tablespoon of vegetable oil in a skillet over medium heat. Add the sliced onions and cook, stirring occasionally, until they are golden brown and crispy around the edges—about 8-10 minutes. Once done, transfer onions to a plate and set aside.
Increase the heat to medium-high and add another tablespoon of oil to the same skillet. Add the ground beef, breaking it apart with a spatula, and cook until it’s browned and cooked through—about 5-7 minutes. Season with salt and black pepper as it cooks.
Once the beef is browned, add the fried onions back into the skillet and mix well. Let the mixture cook together for another minute so the flavors meld and the mixture is heated through.
While the beef mixture finishes, toast the hamburger buns until they are lightly golden—either in a toaster or in a dry skillet for extra crunch.
Use a spatula to scoop generous amounts of the beef and onion mixture onto the bottom half of each toasted bun. Spread evenly for filling every bite with savory goodness.
Cap the sandwiches with the top buns and press down gently to encourage the filling to settle.
Serve the sandwiches hot, with any extra fried onions on top or on the side for added crunch and flavor. Enjoy the hearty, savory mess!
