Preheat the grill to 350 degrees. Cut the loaf of bread in half lengthwise, then cut the top and bottom off.
Place the bread halves on a cutting board and spread cheese slices evenly over each half. Place the top of the bun on each half.
Preheat a large skillet over medium heat and add 1 tablespoon of butter to the pan.
When the butter has melted, place the bread halves onto the skillet and flip after 5 minutes.
After 5 more minutes, remove the bread from the skillet and spread marinara sauce, mozzarella cheese, and pepperonis on the bread.
Place the bread halves back onto the skillet on the same heat setting and let cook for 5 minutes.
Flip the bread over and let cook for an additional 5 minutes, until the cheese has melted. Remove from the heat, slice each half into 4 pieces, and serve. Enjoy!
