Preheat oven to high broil and line a baking sheet with aluminum foil for easy clean up.
Using a serrated knife, cut bread in half vertically in the center and then both pieces horizontally so you have 4 long slices of bread.
Melt butter in the microwave for about 30 seconds (this will depend on the wattage of your microwave). When melted, whisk in garlic powder.
Baste onto cut sides of bread.
Broil for 2-3 minutes, or until bread is toasted. This varies greatly depending on your oven.
Remove and reduce oven temperature to 350 degrees.
Spread marinara sauce evenly onto each piece of bread. Follow with mozzarella cheese and parmesan cheese. Top with pepperoni slices.
Return to oven for 8-10 minutes, or until cheese has melted.
Remove and allow to rest for 1-2 minutes before serving. Pizza will be hot!
If you've tried this recipe come back and let us know how it was in the comments or ratings.
Notes
I find that jarred marinara sauce has more flavor than pizza sauce, but you need to find a thick one. If it is too runny, it will make your pizza soggy. The other alternative is to add 1-2 teaspoons of Italian seasoning to a plain pizza sauce.