Gourmet Hamburger Steaks with Onions and Gravy

I made this recipe up for one of our July 4th cookouts.
It was a really rainy day and I had to cook them inside.
These are simply the best burgers you will ever have.
Everyone goes wild over these,fighting for the last one.

Ingredients
1 pound ground beef
1 egg
1/4 cup bread crumbs
2 tablespoons red wine
1 teaspoon apple cider vinegar
1/8 teaspoon ground black pepper
1/2 teaspoon seasoned salt
1/2 teaspoon onion powder
1/2 teaspoon garlic powder
1 teaspoon Worcestershire sauce
1 tablespoon vegetable oil
1 cup thinly sliced onion
2 tablespoons all-purpose flour
1 cup beef broth
1 tablespoon cooking sherry
1/2 teaspoon seasoned salt
Directions:
In a large bowl, mix together the ground beef,
egg, bread crumbs, pepper, salt, onion powder,
garlic powder, wine, vinegar,and Worcestershire sauce.
Form into 8 balls, and flatten into patties.
Heat the oil in a large skillet over medium heat.
Fry the patties and onion in the oil
until patties are nicely browned, about 4 minutes per side.
Remove the beef patties to a plate, and keep warm.
Sprinkle flour over the onions and drippings in the skillet.
Stir in flour with a fork, scraping bits of beef
off of the bottom as you stir.
Gradually mix in the beef broth and sherry.
Season with seasoned salt. Simmer and stir
over medium-low heat for about 5 minutes,
until the gravy thickens. Turn heat to low,
return patties to the gravy, cover,
and simmer for another 15 minutes.