Preheat your oven to 350°F.

Line an 11x15 baking dish with foil and lightly coat with nonstick spray.

Slice the slider rolls in half and place the bottom halves in the prepared pan.

In a small bowl, whisk together mayonnaise, ketchup, and mustard until smooth.

In a large skillet, heat olive oil over medium heat. Add diced onions and sauté until soft and golden, about 4-5 minutes.

Add ground beef to the skillet with the onions. Cook until no pink remains, breaking up the meat.

Drain excess fat. Add dry French onion soup mix and steak seasoning. Stir well.

Remove from heat and fold in the mayonnaise mixture until evenly coated.

Spread the beef mixture evenly over the bottoms of the slider rolls. Place cheese on top, cutting to fit, then add a pickle slice.

Place the tops of the slider rolls over the filled bottoms. Brush melted butter on top and sprinkle with sesame seeds.

Cover the pan tightly with foil and place on a large cookie sheet. Bake for 15-20 minutes, or until cheese is melted.

Remove from oven and keep covered for 5-10 minutes before uncovering. Serve warm.