In a nonstick skillet, heat a tortilla over medium high heat, open faced for just a minute. Sprinkle 1/4 cup of the cheese all over the tortilla, allowing the cheese to begin to melt. Now place about 1/2 cup of the chicken over the cheese on just ONE side of the tortilla, adding a quarter of the sliced onion on top of that, followed by 1 tablespoon of the cilantro. Fold the tortilla over and mash the top ever so slightly with your spatula to allow the insides to mush together. Repeat with remaining tortillas.