Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine ground beef, chopped onion, garlic powder, Worcestershire sauce, salt, and pepper.
Form the beef mixture into 12 small patties.
Place the patties on a lined baking sheet and bake for 10 minutes.
Top each patty with a slice of cheese and return to the oven for an additional 5 minutes.
Brush the inside of each slider bun with melted butter.
Assemble the sliders by placing a patty inside each bun.
Optionally, add your favorite toppings before serving.