In a mixing bowl, combine ground beef, salt, pepper, garlic powder, and onion powder. Mix until well incorporated. Form the mixture into two large patties.
Heat oil in a skillet over medium-high heat. Place the patties in the skillet and cook for 5–6 minutes on each side until nicely browned and cooked through. Remove the patties and set aside.
In the same skillet, add the sliced onions. Stir frequently for about 5 minutes or until they turn golden and caramelized. Pour in the beef broth and Worcestershire sauce, stirring to incorporate. Bring the mixture to a gentle simmer.
For a thicker consistency, dissolve the flour in a small amount of water, then stir it into the gravy. Continue to simmer until the gravy thickens (optional).
Return the patties to the skillet and spoon the gravy over the top. Let them simmer for an additional 2–3 minutes, allowing the flavors to meld. Garnish with fresh parsley before serving.