In a large bowl, combine olive oil, cumin, paprika, turmeric, garlic powder, onion powder, cayenne pepper, salt, and pepper. Add the chicken thighs and coat them well with the marinade. Cover and refrigerate for at least 30 minutes, or up to 2 hours for more flavor.

Preheat your grill or a skillet over medium-high heat. Cook the marinated chicken thighs for about 5-7 minutes on each side, or until fully cooked and the internal temperature reaches 165°F. Remove from heat and let rest for 5 minutes before slicing.

While the chicken is resting, prepare the vegetables. In a large bowl, combine cherry tomatoes, cucumber, red onion, and parsley. Toss gently to mix.

In a small bowl, whisk together Greek yogurt, tahini, and lemon juice until smooth.

To assemble the bowls, divide the cooked brown rice among four bowls. Top each with sliced chicken, the vegetable mixture, and a drizzle of the yogurt-tahini sauce.