Pre cook your tortillas if they are not cooked already.
Heat a nonstick skillet over medium heat. Make sure all of your ingredients are ready to go as you will be building quickly in the skillet.
When everything is diced and ready, spread 1 1/2 Tbsp of the tzatziki on one side of one tortilla. Put the butter into the skillet.
As soon as the butter is melted, placed the tortilla with the tzatziki in the skillet, tzatziki side up.
Add 1/4 cup of the monterey jack cheese spread out on the tortilla in the skillet.
Sprinkle the cucumber, tomato, olives, onion, and feta around the quesadilla. Add the remaining monterey jack cheese on top.
Place the remaining tortilla on top of it all and press down lightly.
Cover with a lid that at least reaches to the edge of the tortilla. This is to trap in the heat to help melt the cheese without overcooking the tortilla itself.
Cook for approximately 3-4 minutes until the tortilla is lightly browned. With a hand on top of the quesadilla, use a spatula to flip the quesadilla over. It should flip relatively easily as the melted cheese will hold things together and the toasted tortilla will be somewhat stiff and stay parallel to the skillet.
Cover the quesadilla again. Cook on the second side approximately 2-3 minutes until that side is also lightly browned and the cheese is melted. If the tortilla is browning too quickly, turn the heat down. If it is not browning fast enough, you can remove the cover to let out the steam and turn the heat up slightly. Exact results will vary based on your stove and skillet.
Remove the quesadilla and place on a cutting board to rest for 1-2 minutes. The resting will let the cheese start to settle so that it does not all leak out when cut.
Cut the quesadilla into triangles and serve with more tzatziki or hummus.