In a small bowl, whisk together the ground cumin, smoked paprika, ground turmeric, sea salt, black pepper, and garlic powder to create the shawarma spice blend.
Slice the chicken breast into thin, bite-sized strips and toss them in the spice blend until every piece is thoroughly and evenly coated.
Heat the extra virgin olive oil in a medium non-stick skillet over medium-high heat until shimmering.
Add the seasoned chicken strips to the skillet and sauté for 6 to 8 minutes, turning occasionally, until the chicken is golden brown on the outside and cooked through.
While the chicken is searing, dice the cucumber and tomato into small cubes and finely mince the red onion.
In a small ramekin or bowl, stir together the plain Greek yogurt and lemon juice until the sauce is smooth and pourable.
Place the warm cooked brown rice into the bottom of a serving bowl.
Arrange the cooked chicken strips, diced cucumber, tomato, and red onion over the rice base.
Drizzle the creamy lemon-yogurt sauce over the entire bowl and serve immediately while the chicken is still hot.