Preheat oven to 450 -500 F ; Rub Chicken pieces with Lemon. Season throughout with Salt, Pepper. Set aside.
In large skillet, caramelize onions in 2 Tbls of the oil.
Transfer to a blender and puree.
Open up pita so it is one layer thick.
Tear into bite sized pieces.
Line a 10 - 14 inch baking dish/roasting pan with 2/3 of the bread.
Spread pureed onion mixture over the bread. Salt and pepper onion and bread liberally.
Sprinkle 2 Tbls of Sumac over it all.
Place Chicken pieces on top of the bread. Sprinkle 3 Tbls of ground Sumac over the chicken. Add more Salt and Pepper.
Drizzle Olive Oil over the Chicken.
Cover Chicken with remaining bread pieces and drizzle on any remaining Olive Oil.
Squeeze any remaining juice from Lemons over the entire lot. (Option: Drizzle 1/2 cup chicken broth around the edges of the pan.)
Bake for 1 hour. Check every 15 -20 min as it bakes. When bread on top begins to get to dark, Cover loosely with foil.
Cooking time will depend on size of Chicken pieces and oven temp.
Remove bread and mound in the center of a platter. Surround with the Chicken pieces.
Garnish with chopped Parsley & Scallions.