Sprinkle both sides of chicken with taco seasoning mix.
Place chicken in 8 in. square microwave-safe baking dish.
Pour salsa over chicken.
Cover with microwave-safe waxed paper.
Microwave on HIGH for 5 to 9 minutes or until chicken is fork tender and juices run clear, rotating dish once halfway through cooking.
Sprinkle evenly with cheese; microwave on HIGH for 45 to 60 seconds or until cheese melts.
Serve with sour cream.