Pre-heat a large sauté pan over medium-low heat.
Lay a flour tortilla on a cutting board. Spread half of the pizza sauce evenly around the surface of the tortilla.
Place the tortilla in the pan. Turn the heat to low.
Sprinkle the mozzarella and parmesan evenly along one half of the tortilla.
Top the cheese with slices of the pepperoni, evenly distributing them over the top.
Fold the empty side of the tortilla over the top of the cheese and pepperoni, forming a half-moon shape. Gently press down on the top of the tortilla.
Allow the tortilla to cook in the pan, using a spatula to gently lift the corner and check the color. Once the tortilla has a nice golden-brown color to it, gently flip it over, to brown the other side.
Once both sides of the tortilla are browned and crispy, place the pizzadilla on a cutting board.
Pour the remaining pizza sauce into the still hot saute pan, just to warm it up.
Cut into the pizzadilla into wedges. Serve with the hot pizza sauce, as a dip.