Heat skillet over medium heat. Add 1 tbsp butter and let it melt/spread it around the pan. Sprinkle the grated Parmesan in the center of the pan and spread it into an even layer.

Place the tortilla on Parmesan then sprinkle mozzarella evenly across the tortilla. If using, spread a few slices of sun-dried tomato onto the cheese. Spread pesto onto the other tortilla then press it pesto-side down onto the cheese.

Cook until parmesan becomes fragrant and toasted (2-3 minutes) then use a spatula to flip it. Continue cooking for another 2 minutes or until the cheese is melted and the tortilla is toasted.

Repeat for each quesadilla you want to make.

Serve with marinara.