I always make double and cut half the meat and spices/marinade into a gallon freezer bag, give it a good rub and toss in the freezer. It marinates when it thaws.
Sometimes I use tahini instead of toum. Sometimes I use both.
Cut meat into small 1 inches strips. Add marinade ingredients. Allow to marinate; overnight is best. Cook meat in saucepan, medium heat for 45min. If becomes dry, add a little water as needed. Do not overcook.
While meat is marinating, make sauce. Put garlic, salt and 1/4 of lemon juice in blender. Blend on medium then scrape sides. Add egg white, blend on medium. Add half the oil slowly pouring a steady stream. The sauce should emulsify. If it hasn't and looks like it's split, remove half, add another egg white, blend while pouring the half you removed. Switch to slow and add rest of lemon juice then rest of oil slowly. Add 1-2 T water and it should turn creamy and fluffy.
Best if sauce also sits in fridge overnight. Will keep for 1-2 weeks, sometimes longer.
Cut pickles in one inch thin pieces. Slice onion thinly. Slice then half tomato slices.
Add meat to bread then toppings and sauce and enjoy.