In a large pot heat achiote seeds in the canola oil until the oil is orange, 1-2 minutes. Strain through a sieve set over a large bowl and discard seeds. Pour half the oil back into the pot. If you cannot find achiote seeds, substitute 1 t each paprika and turmeric.
To the oil remaining in the bowl, whisk in Chobani, salt and pepper. Add chicken, turn to coat and set aside.
Place the pot of oil over medium-high heat. Add onion, celery, bell pepper and garlic and cook until soft, 8 minutes. Stir in spices and tomato paste and cook 1 minute. Add tomato and cook until juicy, 3-5 minutes, then stir in rice. Add 2¾ c water and the Chobani-chicken mixture. Cook covered over low heat until the rice absorbs all the liquid, 25-30 minutes.
Turn off heat and set aside 15 minutes. Remove chicken and shred, stir back into rice using a fork and serve with cilantro.