Cook the Beef: In a large skillet over medium heat, cook the ground beef until it’s no longer pink. Break the meat into small pieces as it cooks.
Add Aromatics: Add the chopped onion and minced garlic to the skillet. Cook until the onions are translucent and the garlic is fragrant, about 3-4 minutes.
Mix in Pepperoni: Stir the chopped pepperoni into the skillet and cook for another 2 minutes to blend the flavors.
Add Marinara Sauce: Pour the marinara sauce into the skillet. Stir well to combine all the ingredients. Bring the mixture to a simmer.
Season: Sprinkle the Italian seasoning over the mixture and stir. Season with salt and pepper to taste. Let the mixture simmer for about 5-10 minutes, stirring occasionally.
Add Cheese: Reduce the heat to low. Sprinkle the mozzarella and Parmesan cheese over the mixture. Let it melt into the meat, stirring gently to combine.
Prepare the Buns: While the mixture is simmering, toast the hamburger buns until they’re lightly browned and crisp.
Assemble: Spoon a generous amount of the meat mixture onto the bottom half of each bun. If desired, add additional toppings like olives or bell peppers.