Cover achiote seeds with boiling water, cover and set aside overnight.
Drain seeds. Place seeds, 1/2 tablespoon orange juice, vinegar,
cayenne, pepper and garlic in a food processor. Grind until coarse
but mixed well. Place chicken breasts in a shallow dish and cover
with achiote mixture. Marinate in the refrigerator for at least
2 hours.
Preheat grill. Grill chicken about 10 minutes on each side over
a medium flame or until done.