Place a medium skillet over medium heat. Add the pepperoni slices in a single layer and fry until they become crisp and the edges curl.

Transfer the crispy pepperoni onto a plate lined with paper towels to drain excess oil.

Lay four tortillas flat on your workspace. Brush each with an extremely thin layer of pizza sauce.

Sprinkle a generous layer of mozzarella cheese over the sauce on each tortilla.

Evenly distribute the crispy pepperoni on top of the cheese. Add a second thin layer of mozzarella over the pepperoni to help the top tortilla stick.

Brush the remaining four tortillas with a thin layer of sauce and place them on top (sauce side down) to close the quesadillas.

Heat a cast iron skillet or heavy bottomed pan over medium heat and melt a small pat of butter.

Gently place one quesadilla into the pan. Cook for 3 to 5 minutes until the bottom is golden brown and crispy.

Carefully flip the quesadilla and cook for another 3 to 5 minutes until the cheese is completely melted and both sides are golden.

Remove from the pan, let it rest for 60 seconds, then slice into quarters. Serve with a bowl of warm pizza sauce for dipping.