In a large mixing bowl, combine ground beef, breadcrumbs, egg, Worcestershire sauce, garlic powder, onion powder, salt, and pepper until just incorporated.
Form the beef mixture into 4 equal oval patties, approximately 3/4-inch thick.
Heat vegetable oil in a large skillet over medium-high heat and sear patties for 3 to 4 minutes per side until deeply browned. Remove patties from skillet and set aside.
Reduce heat to medium, melt butter in the same skillet, and add sliced onions. Sauté for 8 minutes until softened and golden brown.
Sprinkle flour over the onions and stir for 1 minute to cook out the raw flour taste.
Slowly pour in the beef broth while whisking constantly to prevent lumps, scraping the bottom of the pan to deglaze.
Return the patties and any accumulated juices to the skillet. Simmer uncovered for 10 minutes or until the gravy has thickened and the beef is fully cooked.
Adjust seasoning with salt and pepper to taste and serve hot.