In a large mixing bowl, combine ground chicken, minced garlic, grated onion, parsley, mint, oregano, feta, breadcrumbs, salt, and black pepper. Mix gently for about 2-3 minutes.

Divide into four equal portions and shape each into a patty about ¾ inch thick, making an indentation in the center.

Heat olive oil in a skillet over medium heat for about 2 minutes until shimmering.

Cook patties for 5-6 minutes on each side until golden brown and cooked to an internal temperature of 165°F.

In a small bowl, mix Greek yogurt, grated cucumber, lemon juice, chopped dill, and a pinch of salt and pepper until smooth to create the tzatziki sauce.

Toast the burger buns cut-side down in the same skillet for 1-2 minutes until golden brown.

Spread tzatziki sauce on the bottom half of each bun, add a lettuce leaf, a chicken patty, and fresh tomato slices.