1 (1 1/4 ounce) package taco seasoning
16 ounces boneless skinless chicken breasts
1 cup salsa
1/4 cup fat free sour cream

1  Place chicken breasts and taco seasoning in a seal able plastic bag; shake to coat well.
2  Spray casserole dish with Pam.
3  Place breasts in casserole.
4  Bake 30 minutes at 375 degrees.
5  Top with salsa about 5 minutes before breasts are done.
6  Top with sour cream before serving.

source:   http://www.food.com/recipe/weight-watchers-mexican-chicken-breasts-155442