Preheat the oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish or sheet pan.

In a skillet over medium heat, cook the ground beef, salt, pepper, onion powder, and Worcestershire sauce until the beef is browned and fully cooked. Drain excess grease if needed.

In a small bowl, mix together the mayonnaise, ketchup, mustard, relish, vinegar, and sugar to make the special sauce.

Place the bottom halves of the slider buns in the prepared baking dish.

Spread half of the special sauce over the bun bottoms, then top with the cooked beef, diced onion, shredded lettuce, pickles, and shredded cheddar cheese.

Add the remaining special sauce over the cheese, then place the top halves of the buns on top.

Brush the tops with melted butter and sprinkle evenly with sesame seeds.

Cover loosely with foil and bake for 10 minutes. Remove the foil and bake for 5 more minutes, or until the tops are lightly golden and the cheese is melted.

Let the sliders rest for a few minutes before slicing and serving warm.