Preheat oven to 400 degrees F. Spray the bottom of an appropriately sized glass baking dish.

If the chicken is thawed, place chicken in pan and then spread pesto on top. Bake for 20 minutes then check for doneness.

If chicken is frozen, place chicken in pan and then cook uncovered for 20 minutes, then check for thawedness. If it doesn't seem to have any frosty center, spread pesto on top, bake for a further 20 minutes, then check for doneness.