1-Begin with the preparation: Preheat the oven to 350 degrees Fahrenheit and grease the bottom of a rimmed baking sheet with butter. In a large skillet over medium-high heat, add the olive oil and diced onion, then include the ground beef and break it up with a spatula.

2-Season the mixture: Season the mixture with the salt, black pepper, and garlic powder, cooking until just done before removing from heat. Tilt the skillet to spoon off any excess fat, then stir in the mayonnaise to bind everything together.

3-For assembly: Cut the dinner rolls in half and place the bottom halves on the greased baking sheet, lining them with the sliced medium cheddar cheese. Spread the ground beef mixture evenly over the cheese and top with the shredded medium cheddar cheese.

4-Place the cut-side down top halves of the rolls over the beef mixture.

5-Brush the tops with the melted unsalted butter and immediately sprinkle with the sesame seeds.

6-Bake uncovered for 12 to 15 minutes, or until the cheese melts and the tops are golden brown.