Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Slice the chicken breast into thin strips and place them in a small mixing bowl.
In a separate small bowl, whisk together the olive oil, cumin, coriander, turmeric, garlic powder, smoked paprika, sea salt, and black pepper.
Pour the spice mixture over the chicken and toss until every piece is thoroughly coated.
Spread the chicken in a single layer on the prepared baking sheet and roast for 12-15 minutes, or until cooked through and slightly browned.
While the chicken cooks, dice the cucumber, halve the cherry tomatoes, and thinly slice the red onion.
In a small ramekin, whisk together the Greek yogurt, tahini, and half of the lemon juice to create the sauce.
Toss the cucumber, tomatoes, and onion with the remaining lemon juice and fresh parsley.
To assemble, place the warm cooked brown rice in a bowl, top with the roasted shawarma chicken and the vegetable salad.
Drizzle the creamy tahini-yogurt sauce over the top and serve immediately.