First of all I think it's important to start with a good sharp cheddar. I buy blocks and shred enough to last the week.
Those pre-shredded bagged cheeses do not melt well at all and that's the point, right? A good quesadilla is pure gooey, melty, crunchy goodness.
I know it's crazy but I swear the low carb tortillas such as the Mission Carb balance seem to crisp up better than the regular ones. When I slice into them, I get a satisfying crunch, which is exactly what I want to hear.
Fry up a pound of hamburger meat and add your favorite taco seasoning, preferably homemade. I like to put a little extra cayenne pepper in mine so they have a kick! Let it simmer in some water until most of the moisture is gone.
Spray one side of a tortilla with cooking spray and put down on the griddle or skillet. Top with a small amount of cheese (this is to keep the hamburger mixture from sliding off) then add some taco meat and some more cheese. I like to put some fresh ground pepper on top of the cheese. Top with another tortilla with the spray side up. Cook on both sides until brown and crispy.
Top with salsa and sour cream.