Instructions

• Preheat oven to 350°F. Grease the bottom of a rimmed baking sheet with butter (use additional butter beyond the 2 Tbsp if needed).
• Melt the 2 Tbsp unsalted butter and set it aside to brush the tops later.
• Heat a large skillet over medium-high heat and add 1/2 Tbsp olive oil.
• Add the 1/2 large finely diced yellow onion to the skillet and cook until softened, about 2–3 minutes.
• Add 2 lb lean ground beef to the skillet. Break the beef up with a spatula, then season with 1 tsp salt, 1 tsp black pepper, and 1 tsp garlic powder. Continue cooking over medium-high heat, breaking the meat into small pieces, until no pink remains and the beef is cooked through.
• Remove the skillet from the heat. Tilt the skillet and spoon off and discard any excess fat.
• Stir 1/4 cup mayonnaise into the cooked beef until evenly combined.
• Cut the 24 dinner rolls in half. Arrange the 24 bottom halves in a single layer on the greased baking sheet.
• Place the 8 slices of medium cheddar over the bottom halves, tearing or overlapping slices as needed to cover the buns evenly.
• Spread the beef-and-mayo mixture evenly over the sliced cheese on the bun bottoms, using the back of a spatula to square off the edges.
• Sprinkle 6 oz shredded medium cheddar evenly over the beef layer.
• Place the top halves of the rolls, cut-side down, onto the shredded cheese.
• Brush the roll tops with the reserved melted butter (2 Tbsp), then immediately sprinkle 1 Tbsp sesame seeds evenly over the tops.
• Bake at 350°F for 12–15 minutes, or until the cheese is melted and the tops are golden brown.
• Remove from the oven and let the slider tray cool slightly before serving.