01 - Preheat a grill, grill pan, or skillet to medium-high heat.
02 - Combine ground beef, salt, pepper, and garlic powder in a mixing bowl. Divide into 8 equal portions and shape into patties approximately 2.5 inches in diameter.
03 - Lightly brush cut sides of slider buns with melted butter. Toast cut side down on the grill or skillet until golden, 1–2 minutes. Set aside.
04 - Cook patties 2–3 minutes on the first side. Flip, top each with cheese, and cook 2 minutes more until melted and cooked to desired doneness.
05 - Spread mayonnaise and ketchup on bun bottoms if desired. Place patties, add pickles and optional onion, then top with remaining bun halves.
06 - Serve warm while cheese is still melted.