In a small bowl, combine the cumin, paprika, turmeric, garlic powder, sea salt, and black pepper to create the shawarma spice rub.
Coat the chicken breast thoroughly on both sides with the spice mixture.
Heat the olive oil in a cast-iron skillet over medium-high heat.
Place the chicken in the skillet and sear for 6 to 7 minutes per side, or until the internal temperature reaches 165°F and the exterior is golden brown.
Remove the chicken from the pan and let it rest for 5 minutes before slicing it into thin strips.
While the chicken rests, whisk together the Greek yogurt and lemon juice in a small ramekin until smooth.
Assemble the bowl by layering the cooked basmati rice at the bottom and topping it with the sliced chicken, diced cucumber, diced tomato, and minced red onion.
Drizzle the lemon-yogurt sauce over the top and serve immediately.