Set oven to 350F and spray 9×13 pan with a non stick spray.
Place diced onions on bottom of pan.
Add chicken breasts on top of onions and evenly sprinkle garlic powder and pepper over top.
Place two swiss cheese slices on each chicken breast.
In a medium bowl, mix cream of soup with chicken broth and drained rotel until well combined. Then pour over top of chicken evenly.
Shake bag of stuffing mix over top of chicken.
Pour melted butter on top.
Bake at 350F for 1 hour or until chicken registers above 165F at its thickest part.Let cool for 10 minutes before serving