01 -
Preheat oven to 350°F and butter the bottom of a rimmed baking sheet.
02 -
Heat 1/2 tablespoon olive oil in a large skillet over medium-high heat. Add diced onion and ground beef, breaking up the meat with a spatula. Season with salt, black pepper, and garlic powder. Cook until beef is just done, then remove from heat.
03 -
Tilt the skillet to spoon off excess fat and discard it. Stir mayonnaise into the beef mixture until fully combined.
04 -
Cut rolls in half. Arrange bottom halves on the buttered baking sheet and top each with a slice of cheddar cheese. Spread the beef mixture evenly over the cheese, using a spatula to create an even layer. Cover the beef with shredded cheddar.
05 -
Place the top halves of the rolls, cut side down, over the beef. Brush tops with melted butter and sprinkle with sesame seeds.
06 -
Bake in the preheated oven for 12 to 15 minutes, or until cheese melts and tops are golden brown.