Mix the beef with yogurt, vinegar, olive oil, shawarma spice, and black pepper. Marinate for 2 hours.

Heat the vegetable oil in a skillet and cook the beef until browned and cooked through.

Make the tahini sauce by mixing tahini with garlic, yogurt, lemon juice, and salt.

In a separate bowl, combine the onion with sumac, parsley, and salt.

Serve the shawarma with tahini sauce and the onion-sumac mixture.