Toronto Chicken Shawarma

Name: Toronto Chicken Shawarma
Ingredients: 1 tablespoon ground coriander; 1 tablespoon ground cumin; 1 tablespoon ground cardamom; 1 tablespoon chili powder; 1 tablespoon grill seasoning (such as Montreal Steak Seasoning®); 1 teaspoon smoked paprika; 1/2 teaspoon ground turmeric; 1 lemon, juiced, divided; 1 large clove garlic, minced; 5 tablespoons extra-virgin olive oil, divided; 4 (6 ounce) skinless, boneless chicken breast halves; 1 large onion, sliced; 1 red bell pepper, sliced; 1 yellow bell pepper, sliced; salt and ground black pepper to taste; 1 1/2 cups Greek yogurt; 1/4 cup tahini; 1 teaspoon extra-virgin olive oil; 4 pita bread rounds