Slice the chicken breast into thin, uniform strips and place them in a glass mixing bowl.
Season the chicken thoroughly with cumin, coriander, turmeric, garlic powder, sea salt, and black pepper, ensuring every piece is evenly coated.
Heat the olive oil in a large cast-iron skillet over medium-high heat until it begins to shimmer.
Add the chicken to the skillet in a single layer and sear for 3-4 minutes per side until deeply browned and caramelized.
While the chicken cooks, whisk together the Greek yogurt, tahini, and lemon juice in a small ramekin until the sauce is creamy and smooth.
Layer the warm cooked basmati rice into a serving bowl and top with the hot shawarma chicken.
Add the diced cucumber, halved cherry tomatoes, and minced red onion to the bowl for a fresh, cooling crunch.
Drizzle the tahini-yogurt sauce over the top and serve immediately while the chicken is still sizzling.