Step 1

Make the marinade. To the bowl of a food processor fitted with a blade, add the onion, garlic, sumac, Aleppo pepper, coriander, allspice, lemon juice, and enough olive oil to generously coat the chicken (I used 1/4 cup). Close the lid and pulse several times until well combined into a thick, chunky marinade.

Step 2

Season the chicken. Pat the chicken thighs dry and season very well on both sides with kosher salt and black pepper.

Step 3

Marinate. Place the chicken in a zip-top bag and pour the marinade on top. Close the bag and massage so that all the chicken is well covered with the marinade. Refrigerate anywhere from 30 minutes and up to overnight, turning the bag over occasionally.

Step 4

Grill the lemons and pita bread. Lightly oil the grates and heat your gas grill to medium-high. Arrange the lemon halves cut side down and grill until char marks form. Brush the pita bread with olive oil on both sides. Grill the pita for about 40 seconds per side or until soft and charred. Remove from the heat and set aside.

Step 5

Grill the chicken thighs. Shake excess marinade off the chicken and arrange the chicken thighs on the hot grill. Cover for 5 minutes, then turn the chicken over, cover, and grill until cooked through, another 3 to 5 minutes. Chicken is ready with its internal temperature, taken at the thickest part, is at least 165°F, and its temperature will raise by about 5 degrees as it rests.

Step 6

Rest. Transfer the chicken to a large serving platter and to rest for about 5 minutes.

Step 7

Serve. Sprinkle more sumac on top of the chicken, then pile a handful of pickled onions on top. Add the grilled lemons and pita to one side of the platter next to the chicken. Place the remaining pickled onions and tzatziki sauce in bowls to serve alongside.