While the dipping sauce is simmering, assemble the quesadillas by laying out two tortillas on a cutting board. Sprinkle EACH tortilla with ¾ cup of shredded mozzarella, 1 tablespoon Parmesan, and 2 ounces of diced pepperoni. Lay the remaining tortillas on top.
Heat a large skillet over medium heat. Transfer an assembled quesadilla onto the skillet. Cook for a couple of minutes, occasionally lifting edge of quesadilla to check color of underside, until tortilla begins to turn golden and cheese starts to melt. Carefully flip quesadilla over and cook for another couple of minutes or until cheese is fully melted. Remove hot quesadilla to a plate and repeat with second quesadilla. Alternatively, you may cook both quesadillas at the same time on a flat griddle.
Slice each quesadilla into 6 wedges and serve immediately with warm dipping sauce.
All measurements are approximate. Use as much cheese, etc., as you like!
The pepperoni I typically buy is very large and I prefer to dice it so that the whole piece doesn't pull out of the quesadilla when taking a bite...but leave it whole if you wish.
Feel free to add any of your favorite pizza toppings to the quesadilla filling!