Begin your culinary adventure by preheating your oven to 350°F (175°C). In a small mixing bowl, combine 1½ teaspoons of ground cumin, 1 teaspoon of smoked paprika, 1 teaspoon of salt, and ½ teaspoon of ground turmeric. Stir these ingredients thoroughly to create a fragrant spice mixture that will season your chicken and rice to perfection.
Next, heat 2 tablespoons of extra-virgin olive oil in a large cast-iron skillet over medium heat until it shimmers. Take your four bone-in, skin-on chicken thighs and generously sprinkle them with 2¾ teaspoons of the prepared spice blend. Place the seasoned chicken, skin-side down, into the hot skillet. Cook without moving for 8 to 10 minutes, or until the skin turns a beautiful golden-brown and easily detaches from the pan. Flip the chicken and cook for another 1 to 2 minutes until the other side is lightly browned. Remove the chicken from the skillet and set it aside on a plate.
Utilizing the same skillet, add chopped red onion, chopped red bell pepper, and minced garlic to the residual drippings. Sauté over medium heat, stirring frequently, for approximately 5 minutes until the vegetables have softened. Stir in the two packages of microwaveable brown rice, ¾ cup of water, and the remaining ¾ teaspoon of the spice mixture. Spread this rice blend into an even layer at the bottom of the skillet. Carefully arrange the seared chicken thighs, skin-side up, over the rice mixture. Transfer the skillet to the preheated oven and bake for about 15 minutes, or until the edges are bubbling and an instant-read thermometer inserted into the thickest part of the chicken registers 165°F (74°C). Allow the skillet to rest for 5 minutes before serving.
While the casserole is baking, prepare a creamy tahini drizzle. In a small bowl, whisk together 2 tablespoons of tahini, the remaining 1 tablespoon of water, and the last ½ teaspoon of the spice mixture until smooth. Once the chicken and rice are ready, generously drizzle this flavorful tahini sauce over the entire dish before serving.