In a small bowl, combine the ground cumin, smoked 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 mixture until evenly coated.
Heat the olive oil in a large skillet over medium-high heat.
Add the seasoned chicken to the skillet and sauté for 6-8 minutes, or until the chicken is golden brown and cooked through.
While the chicken cooks, whisk together the Greek yogurt and lemon juice in a small ramekin to create a zesty sauce.
Place the warm cooked brown rice in the base of a serving bowl.
Top the rice with the sautéed chicken, diced cucumber, diced tomato, and minced red onion.
Drizzle the lemon-yogurt sauce over the entire bowl and serve immediately.