- Heat a large frying pan over medium heat. Add the mushrooms, bell pepper, and onion and cook until the mushrooms are tender, 3 to 4 minutes.
- Add the spinach and cook until just beginning to wilt. Remove from the heat and add salt and pepper. Transfer to a bowl. Clean out the frying pan.
- Lay out a tortilla. Spread tomato sauce on half. Top with a quarter of the veggies and a sprinkle of black olives. Drizzle about 3 tablespoons cheese sauce on top and fold over the other side of the tortilla. Repeat with the remaining ingredients.
- Heat the frying pan over medium heat. Spray the pan with olive oil and add 2 quesadillas. Spray the tops of the quesadillas with olive oil.
- After 2 to 3 minutes, when the bottom is golden, flip the quesadillas and cook for 2 to 3 minutes more, until both sides are crispy and golden.
- Place them on a plate and cover with aluminum foil. Repeat with the remaining quesadillas. Slice and serve immediately, with a light drizzle of the cheese sauce over the top and the extra pizza sauce as a dip.
- VARIATION To make these gluten-free, you’ll need some large gluten-free tortillas. Since these tend to break when folded, the method will be a little different.
- Spread the pizza sauce, toppings, and cheese sauce over the entire tortilla, rather than just half. Top with another tortilla and cook as in step 3, repeating to make 2 total. Slice just as you would a normal pizza.