1 small lemon, halved lengthwise and thinly sliced
1 small red onion, cut into 3/4-in. wedges
1/2 cup finely chopped fresh flat-leaf parsley
1/2 cup chopped fresh cilantro
1 tablespoon fresh lemon juice
Preheat oven to 425°F.
Combine 3 tablespoons oil with sumac, 1 teaspoon salt, brown sugar, paprika, and red pepper, and garlic in a medium bowl. Place cauliflower, mushrooms and carrots on a foil-lined baking sheet. Add half of oil mixture; toss to coat.
Add chicken thighs, drumsticks, and lemon slices to pan. Rub remaining oil mixture over chicken.
Bake at 425°F for 20 minutes.
Stir vegetables. Sprinkle onion wedges over pan.
Bake at 425°F for 20 more minutes or until chicken is done.
Combine remaining 3 tablespoons oil, parsley, and remaining ingredients in a small bowl. Spoon parsley mixture evenly over chicken and vegetables.