Jujeh Kebab Spiced Chicken and Tomato Kebabs

Name: Jujeh Kebab (Spiced Chicken and Tomato Kebabs)
Ingredients: 1 cup plain yogurt; 1 ⁄ 2 cup fresh lime juice; 2 tbsp. olive oil; 2 tbsp. orange zest; 1 tbsp. ground cumin; 1 tbsp. kosher salt; 1 tbsp. ground black pepper; 2 tsp. crushed saffron; 1 tsp. ground coriander; 6 cloves garlic, minced; 1 large yellow onion, sliced; 2 lb. boneless, skinless chicken thighs; 4 plum tomatoes, cored; Ground sumac, to garnish; 2 limes, halved; Lavash or pita, for serving