This is a great recipe in a time crunch; it can be put together in fifteen minutes. On a cutting board chop a half an onion. Add a tablespoon of butter to a frying pan and work it around as it melts. Once the pan is well oiled, place a flour tortilla in the bottom of the pan with the heat at a medium setting. Place some cheese slices on the tortilla followed by some slices of ham and top with the chopped onion. Keep in mind to keep all the ingredients spread around evenly so it all melts even. On top of the onions put some more cheese so the top tortilla will stick. Place another tortilla on top of it all, while the one side of the quesadilla is cooking butter the top tortilla by that time it is ready to be flipped and a couple more minutes of cooking on the other side and it is done.