Mix the marinade. In a bowl, whisk olive oil, lemon zest and juice, minced garlic, oregano, cumin, salt, and pepper.
It should smell bright and garlicky.
Prep the chicken. Pat the chicken dry and cut larger pieces into even sizes for quick, even cooking. Add to the marinade, toss to coat, and let it rest for at least 30 minutes or up to 6 hours in the fridge.
Make the tzatziki. Grate the cucumber, then squeeze out excess water with your hands or a clean towel. Stir together Greek yogurt, cucumber, lemon juice, olive oil, dill, garlic, and salt.
Adjust with more lemon or salt to taste. Chill until serving.
Prep veggies. Slice tomatoes, red onion, and rinse your greens. If using olives, pit and halve them.
Crumble the feta so it’s ready to go.
Cook the chicken. Heat a large skillet or grill pan over medium-high. Add a light drizzle of oil. Cook chicken 4–6 minutes per side, depending on thickness, until nicely browned and cooked through.
Let it rest for 5 minutes, then slice.
Warm the pitas. Heat pitas in a dry pan, on the grill, or wrapped in foil in a 300°F oven for a few minutes. Warm bread makes a big difference.
Assemble. Spread a generous layer of tzatziki inside each pita. Add chicken, tomatoes, onion, and greens.
Finish with feta, olives, and herbs. Add an extra spoonful of tzatziki on top.
Serve. Keep napkins handy. A squeeze of fresh lemon over the top brings everything together.