Preheat oven to 350 degrees. Line a large baking sheet with foil.
Make 12 equal size slider patties using your hands or a slider press. Place on baking sheet. Gently press your thumb in the center of each patty slightly to create an indent.
Bake for 15-20 minutes, flipping halfway until cooked through.
Cut cheese slices in half and place a half slice of cheese on each patty and cook a couple more minutes until the cheese is melted. Sprinkle with a pinch of salt.
While the patties are baking, in a small bowl assemble the sauce and buns. In a small bowl mix together the mayonnaise, ketchup and dill relish until combined. Set aside.
Brush butter on the tops of the slider buns and sprinkle with the sesame seeds.
To assemble, place the bottom of the slider buns on a large platter or tray. Top with cooked patties with cheese. Sprinkle with lettuce and diced onion and a pickle.
Spread special sauce on the underside of the top bun and place on top of pickle.
This makes 12 sliders, that will serve about 6 people (2 sliders per person). If you don't need as many, you can easily adjust this and cut the recipe in half.