Step 1

Warm the oil in a large non-stick or cast iron pan over medium heat. Add the onion and saute for a couple of minutes, until it begins to soften. While the onion is cooking, lightly butter one side of each tortilla and set aside.

Step 2

Add the zucchini and the corn to the skillet and continue cooking for a minute or two, until the zucchini is almost tender but still crisp. Add the chicken, if desired, and stir to mix throughout. Transfer the vegetable mixture to a bowl.

Step 3

Return the pan to the stove over medium heat. Place a tortilla in the empty skillet, butter side down. Layer cheese, then the vegetable mixture, and then the remaining cheese onto the tortilla. Top with the second tortilla and let it cook for a couple of minutes.

Step 4

Press down on the top tortilla with a spatula and then carefully flip the quesadilla. Cook for a couple more minutes, until the cheese has melted and the tortillas are crisped and slightly browned.

Step 5

Remove to a cutting board when finished cooking and allow the quesadilla to cool for a minute before slicing and serving.