In a large mixing bowl, combine the ground beef, panko breadcrumbs, egg, Italian seasoning, garlic powder, onion powder, salt, and black pepper. Mix gently with your hands until just combined, being careful not to overmix.

Divide the mixture into 4 equal portions and form each into a 1/2-inch thick patty. Make a slight indentation in the center of each patty with your thumb to prevent them from bulging while cooking.

Heat olive oil in a large skillet or on a griddle over medium-high heat. Once hot, add the burger patties. Cook for 4-5 minutes per side for medium-rare, or longer to your desired doneness. Ensure patties are cooked through to an internal temperature of 160°F (71°C).

While the patties are cooking, slice the burger buns in half. You can lightly toast them in a separate pan, oven, or air fryer for 2-3 minutes until golden.

Once the patties are cooked, reduce the heat to low. Spoon 1 tablespoon of marinara sauce onto the top of each burger patty, spreading it evenly. Top with about 1/4 cup of shredded mozzarella cheese and a few pepperoni slices.

Cover the skillet with a lid or a large piece of foil to allow the cheese to melt, about 2-3 minutes. Alternatively, if your skillet is oven-safe, you can transfer it to a preheated oven at 350°F (175°C) for 2-3 minutes.

Place the cheese-melted burger patties onto the toasted bottom halves of the buns. If desired, sprinkle with grated Parmesan cheese and chopped fresh parsley. Top with the other half of the bun and serve immediately.