Make your pickled onions: place ingredients in a small jar, shake it and chill in the fridge for at least 20 minutes (they'll keep for at least a few weeks).
Pile cheese, greens, jalapeños, cilantro, and a few pickled onions onto tortillas. Heat a skillet over medium heat. Fold the tortillas in half and cook quesadillas for a few minutes on each side, until the cheese is melted.
Enjoy as-is or with toppings of your choice.
Make these gluten free by using gluten free corn tortillas.
Recipe by Love and Lemons at https://www.loveandlemons.com/green-quesadillas/