Similar to a sandwich, the amount of ingredients for a quesadilla depends on how many you are serving and how big you want to make a particular quesadilla. Here are ingredients for one serving using the typical size of tortillas most commonly available in stores in the southwestern U.S. (and in many other areas and countries). Other locally available thin flat breads may work instead of work of tortillas, but please know, the tortillas are intended to be similar to a 'wrap' to allow the eating of the filling.
2 flour tortillas, 6 inches (15 cm) in diameter
⅓ cup grated meltable cheese (preferably a Monterey Jack and cheddar blend or a Tex Mex blend)
¼ cup filling (see options below)
Cooking spray
Salsa
Sarza criolla
Chile peppers
Chopped tomatoes and cilantro
Cooked meat or seafood
Fresh spinach, washed and torn into small pieces
Canned black beans, rinsed and well drained
Warm both tortillas in the microwave to the point of flexibility, keeping one warm.
Preheat a frying pan or griddle over medium-low heat. Grease with oil or cooking spray, and place one of the tortillas in the pan.
Sprinkle the shredded cheese over the tortilla.
Top the cheese with any combination of the fillings, ideally warmed and very well drained. Make sure they are evenly distributed across the tortilla.
Allow the cheese to melt. The tortilla may brown in spots but it should not be cooked to the point of changing color substantially.
Press the other tortilla over the top of the tortilla in the pan, making sure it sticks a bit.
Flip the quesadilla and allow to warm until it joins as a unit.
Remove from pan and cut in eight wedges.
Eat immediately, or remove to a fairly low-temperature 'keep warm' area, below the melting temperature of the cheese.