Prepare the Marinade: Combine grated and strained onion, yogurt, salt, black pepper, and a tiny amount of strained zatar in a bowl to make the marinade.
Marinate the Meat: Create layers of thinly sliced veal and lamb in a Tupperware, applying the marinade between each layer. Close the Tupperware and let it marinate in the fridge for at least 24 hours.
Freeze the Meat: After marinating, transfer the meat to the freezer for at least 2 hours until it is completely frozen.
Slice the Meat: Remove the frozen meat from the freezer and cut it into thin slices, mimicking doner kebab slices.
Cook the Meat: Fry the meat slices in a pan, optionally using lamb fat for added flavor, until they are crispy yet juicy.
Serve: Serve the cooked meat slices on bread or as desired. Enjoy the homemade doner kebab that closely replicates the authentic flavors experienced in Istanbul.