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
Preheat an indoor or outdoor grill for high heat, and lightly oil the grate.
Whisk together the coriander, cumin, cardamom, chili powder, grill seasoning, paprika, and turmeric in a bowl; whisk in juice of 1/2 lemon, garlic, and 3 tablespoons olive oil to form a paste. Coat the chicken breasts with the spice paste.
Grill chicken breasts on the preheated grill until juices run clear and chicken is no longer pink at the center, about 6 minutes per side. Transfer chicken to a plate and cool for 1 to 2 minutes; slice thinly.
Heat 2 tablespoons olive oil in a large skillet over medium-high heat. Stir onion, red pepper, and yellow pepper into the hot olive oil; season with salt and pepper. Cook, stirring frequently, until the vegetables are tender, about 5 minutes.
Stir together Greek yogurt, tahini, juice of remaining 1/2 lemon, and remaining 1 teaspoon olive oil in a bowl until smooth; season with salt.
Place pitas on the grill until heated through and lightly charred on the outside, about 1 minute per side. To assemble each sandwich, place some sliced chicken on each pita; top with some of the pepper mixture and a good dollop of yogurt tahini sauce.