In a small bowl, combine the cumin, paprika, turmeric, garlic powder, sea salt, and black pepper to create the shawarma spice rub.
Cut the chicken breast into bite-sized pieces and toss thoroughly with the spice blend until evenly coated.
Heat the olive oil in a large skillet over medium-high heat and sauté the chicken for 6-8 minutes until golden brown and cooked through.
While the chicken cooks, whisk together the Greek yogurt, tahini, and half of the lemon juice in a small ramekin to make the sauce.
In a separate bowl, toss the diced cucumber, tomato, and red onion with the remaining lemon juice for a quick salad.
Assemble the bowl by placing the warm cooked brown rice at the bottom, then top with the spiced chicken and the fresh vegetable salad.
Drizzle the creamy tahini-yogurt sauce over the top before serving.