Combine the yoghurt, vinegar, garlic, pepper, salt, cardamon pods, Lebanese 7 Spice and Lemon juice to make the marinade. If it seems a little dry, add a little olive oil (a tablespoon at a time).
Prepare the Chicken
Add chicken, cover and refrigerate at least 8 hours, preferably overnight.
In a stockpot or large saucepan, cook chicken over medium heat for 45 minutes or until done. Be sure not to overcook! If chicken becomes a little dry, add a few tablespoons of water throughout cooking duration.
While chicken is cooking, prepare the sauce.
Prepare the Sauce
Combine sauce ingredients and mix well. Set aside.
Prepare the Pita
Take the onions, tomatoes, cucumbers and sprinkle with sumac.
When the chicken is done, cut into thin slices.
Place enough chicken on pita that cover 1/4 of the loaf.