In a bowl, place the meat strips and all the marinade ingredients together. Mix well and let it marinate in the refrigerator for at least 2 hr.

Transfer the beef and its marinade to a baking tray, mix in the onion slices and layer with the tomato slices on top.

Cover the tray with aluminum foil and place it in the oven on medium heat for 1 hr or until the meat is well done.

To prepare the tahini sauce: with a spoon, mix the tahini with water until you get a smooth texture. Add the crushed garlic, lemon juice and salt. Mix again until you get a fluid sauce. Adjust lemon and salt to taste.

Beef shawarma is best served with chopped fresh parsley sprinkled with sumac, along with tarator sauce and pita bread.

Note: You can replace ¼ cup of the apple cider vinegar with ½ cup of red wine.
You can find the recipe 'tahini sauce' in this application.