01 - Combine Greek yogurt, grated cucumber, dill, garlic, lemon juice, olive oil, salt, and pepper in a medium bowl. Stir thoroughly until incorporated, cover, and refrigerate until ready to serve.
02 - Combine ground chicken, breadcrumbs, feta cheese, red onion, parsley, minced garlic, oregano, cumin, salt, and pepper in a large bowl. Mix gently until just combined—avoid overworking the meat to maintain texture.
03 - Divide the chicken mixture into 4 equal portions and shape each into uniform burger patties, approximately ¾ inch thick. Create a slight indentation in the center of each patty to prevent puffing during cooking.
04 - Heat olive oil in a large skillet or grill pan over medium heat. Place patties in the pan and cook for 5–6 minutes per side until golden brown and cooked through, reaching an internal temperature of 165°F.
05 - Place lettuce leaves on the bottom half of each toasted bun. Top with a cooked chicken patty, followed by tomato slices, red onion rings, and a generous spoonful of chilled tzatziki sauce. Cover with the top bun and serve immediately.