In skillet, cook 1 sliced onion in 2 tbsp. butter over medium heat, stirring, until caramelized, about 25 minutes.
Position a rack in the upper third of the oven; preheat to 400°. Line a baking sheet with foil; coat with cooking spray. Using a food processor, pulse the pita bread into crumbs; in a bowl, combine with the milk. Let sit for 5 minutes.
Combine the pita bread breadcrumbs, ground chicken, 1 grated onion, garlic, egg, dried apricots, raisins, turmeric, 1 tsp. salt and 1/2 tsp. pepper. Shape into a 5-by-8-inch rectangle on the sheet.
Bake, coating with caramelized onions halfway through, until a thermometer inserted in the center registers 170°, 50 minutes. Let rest for 10 minutes before slicing.