01 - Combine Greek yogurt, grated cucumber, minced garlic, dill, lemon juice, olive oil, salt, and pepper in a bowl. Mix thoroughly, cover, and refrigerate until ready to serve.
02 - Combine ground chicken, red onion, garlic, feta cheese, parsley, dill, oregano, cumin, salt, and pepper in a large bowl. Mix gently until just incorporated, being careful not to overwork the meat mixture.
03 - Shape the seasoned chicken mixture into 4 equal patties, approximately 1/2 inch thick, ensuring uniform size for even cooking.
04 - Heat olive oil in a grill pan or skillet over medium heat. Cook patties for 5–6 minutes per side until golden brown and fully cooked through, reaching an internal temperature of 165°F.
05 - Lightly toast burger buns or pita breads on the grill pan or in a toaster until golden and slightly crispy.
06 - Layer crisp lettuce on the bottom bun, place a cooked chicken patty on top, generously spoon tzatziki sauce over the patty, and add tomato and red onion slices. Finish with the top bun.
07 - Serve burgers immediately while hot, with extra tzatziki sauce on the side for dipping.