In a large mixing bowl, combine the ground beef, breadcrumbs, egg, onion powder, garlic powder, salt, and black pepper. Mix by hand until just combined; do not overwork.
Form the mixture into four equal-sized oval patties, approximately 3/4-inch thick.
Heat the vegetable oil in a large skillet over medium-high heat until shimmering.
Add the patties to the skillet and sear for 3 to 4 minutes per side until a brown crust forms. Remove patties from the pan and set aside on a plate.
Add the sliced onions to the same skillet and cook over medium heat, stirring frequently, until they are softened and lightly caramelized (about 5-7 minutes).
Sprinkle the flour over the onions and cook for 1 to 2 minutes, stirring constantly to incorporate with the fat.
Slowly pour in the beef broth and Worcestershire sauce while whisking or stirring constantly to prevent lumps.
Bring the gravy to a simmer. Once thickened, return the beef patties and any accumulated juices to the skillet.
Reduce heat to low, cover, and simmer for 5 to 10 minutes until the patties are cooked through to an internal temperature of 160°F (71°C).
Serve the patties immediately, smothered with the onion gravy.