Preheat oven to 350. In a large saucepan over medium heat and stirring often, heat both soups, chopped onion, rotel tomatoes, and jar of cheez whiz, until well blended. Reduce to simmer. Add cooked, shredded or cubed chicken. Stir well.
Soak tortillas in chicken broth for a few minutes. Layer bottom of 9 x 13 pan with tortillas. (It is okay to overlap).
Top the tortillas with the chicken/sauce mixture. Repeat each layer.
Top with shredded cheddar cheese. Bake at 350 degrees for 45 minutes. Enjoy! Very tasty!