Sheet Pan Chicken with Zaatar, Carrots, and Avocado

2 pounds boneless, skinless chicken thighs
1 pound carrots, peeled and sliced 1/8-inch thick on the diagonal
1/2 large red onion, sliced 1/4-inch thick
2 tablespoons za’atar
1 lemon, zest and juice reserved
1 pinch kosher salt, plus more to taste
1 pinch freshly ground black pepper, plus more to taste
2 teaspoons honey
4 tablespoons plus 2 teaspoons olive oil, divided
2 ounces feta, crumbled or thinly sliced
1/4 cup pistachios, finely chopped/crushed into irregular pieces with a knife
1 teaspoon sumac (optional)
1 cup watercress, arugula, or spinach
1 large ripe avocado, sliced

Heat oven to 425 degrees Fahrenheit. Place a parchment-lined sheet pan in the oven while it heats.
In a large bowl, combine chicken, carrots, onions, za’atar, lemon zest, 2 teaspoons kosher salt, pepper, honey, and 4 tablespoons olive oil. Toss well with hands to evenly coat the chicken and vegetables in the olive oil and seasonings. (This step can be done 6 to 8 hours in advance; cover and refrigerate until ready to use.)

Working quickly, empty the contents of the bowl on the hot sheet pan, then arrange the ingredients in a single, even layer. (Careful, the pan will be hot!)
Roast for 12 minutes, then flip the chicken and stir the carrots. Roast for another 8 to 10 minutes, or until the chicken is cooked through (internal temperature should be 165 degrees Fahrenheit in the thickest piece). Remove from oven.

Meanwhile, in a small bowl, mix together the feta, pistachios, and 2 teaspoons of olive oil. Set aside.

Heat the broiler with an oven rack about 4 to 5 inches from the heating element. Broil the chicken and carrots for 1 to 2 minutes, or until they’re starting to brown and crisp around the edges.
Immediately out of the oven, squeeze the juice from half the lemon, and sprinkle the sumac (if using) over the entire dish.

Let cool for about 5 minutes, then toss in the watercress, feta and pistachios, and avocado. Serve warm.