Make the Special Sauce
In a small bowl, mix mayonnaise, sweet pickle relish, sugar, mustard, paprika, onion powder, and garlic powder.
Stir until well combined and refrigerate until needed.
Cook the Beef
In a large skillet over medium heat, cook the ground beef and chopped onions.
Season with salt and black pepper, breaking up the beef as it cooks.
Drain any excess grease and set aside.
Assemble the Sliders
Preheat the oven to 350°F (175°C) and lightly grease a 9×13-inch baking dish.
Place the bottom halves of the slider buns in the dish.
Spread a thin layer of the special sauce over the bun bottoms.
Evenly distribute the cooked beef mixture over the sauce.
Layer American cheese slices over the beef.
Add dill pickle slices on top of the cheese.
Bake the Sliders
Cover the dish with aluminum foil and bake for 10 minutes, until the cheese melts.
Add the Finishing Touches
Remove the foil and sprinkle shredded lettuce over the sliders.
Spread additional special sauce on the top buns, then place them over the lettuce.
Brush the tops of the buns with melted butter and sprinkle with sesame seeds.
Return to the oven for an additional 3-5 minutes, until the buns are slightly toasted.
Serve and Enjoy
Let the sliders cool slightly, then slice and serve warm.