Stay away from the microwave. Using a microwave will result in a limp, unevenly heated quesadilla, and that would make everyone sad. Properly reheating leftover quesadillas takes a bit of time - you want to be sure that the inside gets warm and melty, and the outside gets crisped up again, without getting burned. You have two options: oven or stovetop. Our preference is the stovetop because it's easier to watch for burning and simpler to control the heat. Here's what to do: 1. Slick a skillet with a little bit of oil, then let it warm up over medium-low heat for a few minutes. 2. Add the quesadilla, heating it for about a minute. You'll probably need to flip it several times, but don't leave either side down for very long. If you notice one side getting too browned, turn your heat down and continue flipping. 3. If your quesadilla is thick and super packed, you may need to cover the skillet with a lid to retain heat and get the insides all gooey and delicious. Still, flip it every minute or so.