Marinate the chicken. In a bowl, whisk together yogurt, olive oil, garlic, lemon zest, lemon juice, oregano, cumin, paprika, coriander, salt, and pepper. Add chicken and coat well.
Cover and refrigerate for at least 30 minutes, ideally 2–4 hours for deeper flavor.
Make the sauce. Combine yogurt, grated cucumber (squeeze out water), lemon juice, garlic, dill, salt, and pepper. Stir until creamy. Chill until serving so flavors meld.
Prep the veggies and base. Cook your chosen base (cauliflower rice for ultra-light, quinoa or brown rice for more staying power).
Chop tomatoes, cucumber, onion, and greens. Set aside.
Cook the chicken. Heat a cast-iron skillet or grill pan over medium-high. Lightly oil the surface.
Cook chicken 4–6 minutes per side, depending on thickness, until golden with some char and the internal temp hits 165°F (74°C). Rest 5 minutes, then slice.
Assemble the bowls. Add base to each bowl. Top with greens, tomatoes, cucumber, onion, olives, and sliced chicken.
Spoon over tzatziki. Finish with a squeeze of lemon and a sprinkle of feta if using.
Adjust to taste. Add a drizzle of olive oil, extra dill, or a pinch of kosher salt. If you like heat, a few red pepper flakes work nicely.