Thinly slice your beef into strips (freezing your meat helps make this even easier) and add the meat to a large bowl.
Gather the grated onion into a kitchen towel or cheesecloth and squeeze all the juice out of the onion and into a bowl. Reserve the grated onion for another use and add the onion liquid to the bowl with the beef.
Add the lemon juice and yogurt to the beef, then all the spices. Mix the meat with the marinade ingredients until everything is evenly coated and combined, then let sit for at least 1 hour.
Preheat your broiler on high and add a sheet tray into the oven to heat up with the broiler so when you add the meat to the pan it’s already hot and sizzling.
Remove the preheated sheet tray from the broiler and spread with an even layer of beef tallow or cooking oil. Add the marinated beef in an even layer and then put back into the broiler on high for about 5-7 minutes, or until the beef is cooked through and nicely browned.
To serve: warm up the pita bread, add a layer of juicy beef shawarma meat, sliced tomatoes, sumac onions, chopped parsley, tahini sauce, a drizzle of pomegranate molasses, and serve with shatta hot sauce on the side.
