Slice the chicken breast into thin strips and place them in a medium mixing bowl.
Toss the chicken with the cumin, coriander, turmeric, garlic powder, paprika, salt, pepper, and half of the lemon juice until evenly coated.
Heat the olive oil in a large skillet over medium-high heat until shimmering.
Add the chicken to the skillet and sauté for 6 to 8 minutes, stirring occasionally, until golden brown and cooked through.
While the chicken is cooking, combine the diced cucumber, cherry tomatoes, red onion, parsley, and apple cider vinegar in a small bowl to create the salad.
In a separate small jar or bowl, whisk together the tahini, remaining lemon juice, and water until the sauce is smooth and creamy.
Place the warm cooked brown rice in the base of a serving bowl.
Arrange the sautéed shawarma chicken and the fresh vegetable salad over the rice.
Drizzle the tahini sauce over the entire bowl and serve immediately.