In a large mixing bowl, combine the ground lamb or beef, chopped onion, minced garlic, dried oregano, ground cumin, salt, and black pepper. Mix well until all ingredients are fully incorporated.

Shape the Meat

Form the meat mixture into elongated patties or loaves, approximately 1/2 inch thick.

Cook the Meat

Heat a grill or skillet over medium-high heat. Cook the meat patties for about 5-7 minutes on each side, or until fully cooked and browned.

Prepare the Pita

Warm the pita bread on the grill or in a dry skillet for about 1-2 minutes on each side until softened.

Assemble the Gyros

Place a cooked meat patty in the center of each pita. Top with sliced tomato, cucumber, a generous dollop of tzatziki sauce, and sprinkle with chopped parsley.

Serve

Fold the pita around the filling and serve immediately, optionally with extra tzatziki on the side.