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 serving.
02 - Combine ground chicken, red onion, garlic, feta, parsley, dill, oregano, cumin, salt, and pepper in a large bowl. Mix gently until just incorporated, avoiding overworking the meat.
03 - Shape the mixture into 4 equal patties, ensuring uniform thickness for even cooking.
04 - Heat olive oil in a grill pan or skillet over medium heat. Cook patties 5-6 minutes per side until golden brown and fully cooked through, reaching internal temperature of 165°F.
05 - Lightly toast burger buns or pita breads until warm and slightly crisp.
06 - Layer lettuce on bun base, add chicken patty, spoon generous tzatziki over top, and finish with tomato and onion slices. Place top bun and serve immediately with extra tzatziki on the side.