Combine onion, 1 tablespoon of lemon juice, salt, cumin and sugar in a large bowl. Stir well and let the mixture rest for at least 10 minutes as you get the other ingredients ready.
In a small bowl, combine tahini, garlic, a pinch of salt and the remaining 1 tablespoon of lemon juice. Add 2 to 3 tablespoons of warm water to make the sauce thinner. It should be pourable but not runny. Adjust the salt and lemon juice to your taste.
Add the onions, cucumbers, tomatoes and oil to the bowl. Mix well and season with salt and lemon juice to your liking.
Pro Tip: To make the chicken more blackened and crispy, flash pan-fry it. Heat some neutral oil in a hot pan until it smokes. Then, add the chicken and leave it for a minute to create some texture. This will give the pita an authentic street-food vibe. However, you can also use cold chicken and enjoy it.
To heat the pita bread, you can either bake it in the oven briefly or toast it in a skillet.
To assemble each pita sandwich, start with some chicken pieces and pour some tahini-lemon sauce over them. Next, add some chickpea salad and sprinkle cilantro and mint on top. Finish with more tahini sauce as desired.Pro Tip: Lebanese bread works great also! You can enjoy this dish with fries and a green salad, or any other side dish of your choice.