Freeze your steaks for an hour or two to firm up before slicing.
With a sharp knife, thinly slice your steaks across the grain to thin slices and transfer to a bowl and let it sit to defrost for 20 minutes.
Add vinegar, yogurt, all mentioned spices, 1 pack Knorr Beef Flavored Stock Powder, and oil, and mix well till all ingredients coat the thin strips of meat.
Cover and marinate for at least 1 hour to 24 hours in the fridge.
For Tahini Sauce, in a bowl, add tahini, yogurt, vinegar, lemon juice, minced garlic, salt and whisk till incorporated and smooth.
In a nonstick pan, add a touch of oil and stir fry your shawarma in batches 3-5 minutes till the edges are crispy.
Build your sandwich in a piece of pita bread, add tomatoes, pickled onions, sumac, tahini sauce, parsley, and a drizzle of pomegranate molasses. Wrap your sandwich and enjoy.