Preheat the oven to 375° F. Spray a 9x13-inch baking dish with non-stick spray.
Sprinkle the seasoning mix on both sides of the chicken breasts. ( I cut the chicken into chunks and toss them with the taco seasoning.) Place the seasoned chicken breasts in the prepared dish.
Pour Rotel ( or salsa) on top of the chicken.
Bake in the preheated oven until the chicken is tender and juicy, and the juices run clear, 25 to 35 minutes.
Sprinkle chicken evenly with cheese.
Return the dish to the oven and bake for another 3 to 5 minutes, or until the cheese is melted and bubbly.
Let the chicken rest for a few minutes before serving. Spoon some of the tomatoes and juices from the baking dish when serving.
Top with sour cream or guacamole if desired.