Preheat the oven to 350°F (175°C) and generously grease a 9x13-inch baking dish to prevent sticking.
Melt the butter in a large skillet over medium heat. Add the ground beef, cooking until it’s browned and fully cooked. Drain any excess fat.
Season the beef by mixing in onion powder, garlic powder, salt, and pepper. Stir well to coat the meat evenly.
Combine the cooked beef with the cooked rice, condensed French onion soup, and sour cream in a mixing bowl. Stir until well incorporated.
Spread the beef and rice mixture evenly in the prepared baking dish. Top with shredded mozzarella cheese.
Bake for 25-30 minutes, until the cheese is melted and golden brown.
Garnish with chopped parsley before serving.