Slice the lamb into thin strips.

In a large bowl, combine olive oil, lemon juice, salt, black pepper, shawarma spice mix, and 1 tablespoon of vinegar. Mix well, cover, and refrigerate overnight.

Preheat the oven to 400°F (200°C).

Chop the tomato and add it to the marinated lamb. Place the lamb mixture on a baking sheet and bake until cooked through.

To make the dressing: In a bowl, combine lemon juice, tahini, vinegar, and yogurt. Mix well, then add the minced garlic.

Slice the onion into thin strips, then rub the sumac into the onion.

Use a round cutter to cut the tortilla bread into circles.