Slice the chicken breast into thin, even strips and place them in a medium mixing bowl.
Add the cumin, smoked paprika, turmeric, garlic powder, onion powder, sea salt, black pepper, and lemon juice to the chicken, tossing thoroughly to coat.
Preheat a high-quality non-stick skillet over medium-high heat. To keep the recipe lean, avoid adding oil; the lemon juice and moisture from the chicken will prevent sticking if the pan is well-heated.
Add the chicken strips to the skillet in a single layer and sear for 3-4 minutes per side until deeply browned and cooked through.
While the chicken cooks, prepare the bowl base by layering the shredded romaine lettuce, diced cucumber, and thinly sliced red onion.
Place the hot shawarma chicken over the fresh vegetables.
Top the bowl with a dollop of non-fat Greek yogurt to serve as a cooling, high-protein sauce.