Get a 9x13in pan with depth. Mine is glass that looks like a rectangular cake pan

Cut the onion and sautee in a pan until caramelized.

Pour some enchilada sauce into the pan, just enough to coat the bottom

Put the rest of the enchilada sauce in a saucepan and warm on the stove.

Dip the tortillas in the green sauce and make a layer of corn tortillas in the pan.

Sprinkle the chicken, cheese and caramelized onion. Dip more corn tortillas into the green sauce and create another layer

Add chicken cheese and onion until you don't have ingredients or the pan is full. Sprinkle cheese on top and put the rest of the sauce into the pan.

Warm in the oven at 350 degrees F for a few minutes until the cheese is melted.