In a mixing bowl, combine the lemon juice, olive oil, minced garlic, dried oregano, ground coriander, ground cumin, salt, and pepper. Add the chicken thighs to the marinade, ensuring they are well coated. Cover the bowl and let it marinate in the refrigerator for at least 30 minutes.
In another bowl, mix together the Greek yogurt, mayonnaise, additional lemon juice, granulated sugar, and garlic powder. Stir until smooth and creamy. Set aside in the fridge to chill while you cook the chicken.
Heat a grill pan or skillet over medium-high heat. Add a tablespoon of butter to the pan. Once melted, add the marinated chicken thighs. Cook for 5-7 minutes on each side, or until the chicken is cooked through and has a nice golden-brown color. Remove from heat and let rest for a few minutes before slicing.
In a pot, combine the basmati rice, chicken base or bouillon, turmeric, onion powder, ground cumin, and water. Bring to a boil, then reduce heat to low, cover, and let simmer for about 15-20 minutes, or until the rice is tender and the water is absorbed. Fluff with a fork before serving.
On a large serving platter, layer the fluffy rice, sliced chicken, shredded lettuce, and diced tomatoes. Drizzle the creamy sauce over the top and garnish with fresh parsley. Serve with pita or naan strips on the side and a drizzle of harissa hot sauce for an extra kick.