Preheat oven to 425 degrees F. Line a rimmed baking sheet with parchment paper.
Split the hamburger buns in half and arrange them cut-side-up on the pan. Spread a spoonful of the sauce over each half and top with shredded cheese and pepperoni (if using).
Bake for 10 to 15 minutes, or until the cheese is completely melted and the edges of the buns are starting to toast.