In a bowl, combine the chicken pieces with yogurt, lemon juice, olive oil, cumin, coriander, turmeric, paprika, garlic powder, onion powder, cinnamon, cardamom, cayenne (if using), salt, and pepper. Mix well to coat the chicken completely.
Cover the bowl and marinate the chicken in the refrigerator for at least 30 minutes, or up to 4 hours for deeper flavor.
Pour 1/2 cup of water into the bottom of your Instant Pot liner.
Place the marinated chicken mixture into a heat-safe bowl or trivet insert that fits inside the Instant Pot. Do not place the chicken directly on the bottom of the pot.
Place the trivet or bowl inside the Instant Pot. Secure the lid and set the valve to sealing.
Pressure cook on High for 8 minutes.
Once cooking is complete, allow for a Natural Pressure Release (NPR) for 5 minutes, then manually quick release any remaining pressure.
Carefully remove the chicken and set it aside. The sauce remaining in the pot will be used for the rice.
Rinse the rice thoroughly. In a separate bowl, mix the rinsed rice with the chicken broth.
Pour the rice and broth mixture into the Instant Pot liner (discarding the water used for pressure cooking if necessary, or carefully pouring the broth mixture over the cooked chicken juices if you want maximum flavor, ensuring you do not exceed the max fill line).
Place the trivet back in the pot, place the bowl of cooked chicken on top of the trivet, and add the rice mixture underneath. Secure the lid.
Pressure cook on High for 4 minutes with a Natural Pressure Release (NPR) of 10 minutes, followed by a quick release.
Fluff the rice gently with a fork. Serve the Instant Pot Chicken Shawarma immediately over the cooked rice, adding your preferred toppings.
Notes
For a more traditional texture, you can briefly broil the cooked chicken pieces under a broiler for 2-3 minutes after pressure cooking until the edges brown slightly.
If you prefer to cook the rice separately on the stovetop, reduce the Instant Pot cooking time for the chicken to 6 minutes with a 5-minute NPR.
Tahini sauce is made by whisking tahini paste, lemon juice, garlic, and water until smooth.