Preheat the oven to 350°F (175°C).
In a skillet, cook ground beef over medium heat until browned. Drain any excess fat.
Add diced onions, salt, pepper, and garlic powder to the beef and cook until onions are softened.
Slice the slider rolls in half horizontally. Place the bottom half on a baking tray.
Spread mayonnaise and ketchup evenly over the bottom layer of rolls.
Layer the cooked beef mixture on top, followed by slices of cheddar cheese.
Place the top half of the rolls over the cheese.
Brush melted butter over the top of the rolls and sprinkle with sesame seeds.
Bake in the oven for 15 minutes, or until the cheese is melted and sliders are heated through.
Slice and serve warm!