Preheat oven to 375°F. Place chicken breasts in a lightly greased 9x13 inch baking dish. Sprinkle taco seasoning on both sides of chicken breasts, and pour salsa over all.

Bake at 375°F for 25 to 35 minutes, or until chicken is tender and juicy and its juices run clear.

Sprinkle chicken evenly with cheese, and continue baking for an additional 3 to 5 minutes, or until cheese is melted and bubbly. Top with sour cream and serve.