In a large bowl, whisk together yogurt, lemon juice, tandoori masala, cumin, paprika, coriander, salt, pepper, garlic, ginger, and tomato sauce until smooth.

Add the chicken thighs to the bowl, turning to coat them evenly in the mixture.

Cover the bowl, cover with plastic wrap, and refrigerate for at least 1 hour (or overnight for deeper flavor).

Place the marinated chicken and any remaining sauce into the slow cooker.

Cook on low for 7 hours (420 minutes).

While the chicken cooks, rinse the rice under cold water until the water runs clear.

In a saucepan, bring the water to a boil, add rice and 0.5 tsp salt, cover, reduce heat to low, and simmer for 18 minutes, then let stand covered for 5 minutes.

When the chicken is finished, remove from the slow cooker, shred with two forks or serve whole, and sprinkle with fresh cilantro.

Serve the chicken over the fluffy rice, and check that the chicken has reached a safe internal temperature with a food thermometer before serving.