Heat a large skillet over medium heat. Spray with non-stick cooking spray.
Place a flour tortilla in the center in the center of the skillet.
Add cheese to one half. Lay the pepperoni, onions, and preferred toppings on top of the cheese. Fold the empty tortilla half over the filled side. (You could also saute the onions first, if you prefer them softer.)
Cook for about 2 minutes on each side. Repeat with remaining tortillas.
Slice with a pizza cutter. Heat marinara or pizza sauce, if desired.
Prepare fresh veggies.
Serve Pizzadillas with a side of sauce and fresh veggies.