Crush a pinch of saffron using a mortar and pestle. Transfer to a bowl and add warm water. Let it soak for 15 to 20 minutes until it turns a rich yellow/orange color.
**Prepare the Chicken & Baste:**
In a bowl, combine the cubed chicken with 2 tablespoons of saffron water, black pepper, smoked paprika, salt, lemon juice, yogurt, olive oil, minced garlic, and grated yellow onion. Mix well and marinate for 30 minutes to overnight.
Thread the marinated chicken onto skewers, about 5 to 6 pieces per skewer. If using wooden skewers, soak them in water for 30 minutes to prevent burning.
Mix melted butter, lemon juice, saffron water, and black pepper for the baste. Set aside.
**Cooking:**
Preheat the oven to 450°F. Arrange the skewers on a baking tray and roast for about 20 minutes or until cooked through, basting with the flavored butter halfway through.
For a charred look, broil the skewers for a few minutes after roasting, basting again before serving.
Serve the skewers on a plate lined with lavash bread, drizzle with pan juices, and sprinkle with sumac or Aleppo pepper. Enjoy the flavorful feast!