This is fabulous chicken. The olive brine in the marinade and the sumac spice make for a very flavorful meal. The texture and sweetness from the relish bring it all together perfectly. 
This is an ideal dish to make to get out of your usual chicken dinner rut. 
4 bone-in skin-on chicken thighs
1 lemon zested and juiced
⅓ cup olive brine
¼ tsp red pepper flakes
6 sprigs of tarragon, leaves removed and chopped
½ tsp salt
3 Tbsp olive oil
½ red onion, sliced
10 oz. carrots, peeled and sliced
2 tsp sumac
Pinch of pepper
½ small red onion, thinly sliced
6 dates, pitted and chopped
⅓ cup pistachios, chopped
¼ cup chopped Italian parsley
¼ cup green olives, pitted and chopped
1 lemon zested and juiced
Salt and pepper
To make the marinade, place the zest and juice of one lemon, olive brine, red pepper flakes, tarragon, and ½ tsp salt into a bowl and stir. 
Score the flesh side of the thighs and add the chicken to the marinade. Let sit for 1 - 3 hours in the refrigerator. 
Preheat oven to 425℉
Make the relish by adding the onion, dates, pistachios, parsley, green olives, lemon zest, and lemon juice to a bowl. Season with salt and pepper to taste and set aside.
Heat the olive oil in a cast-iron skillet or another oven-proof skillet over medium-high heat. Place the marinated chicken into the skillet skin side down. Cook without turning until the chicken is caramelized and crisp. Approximately 7 minutes. Turn the chicken over, season with salt and pepper, and transfer to a plate. 
Next, add the onion, carrots, and sumac to the skillet, season with salt and pepper, and stir to coat. Return the chicken, skin side up, to the skillet. Place the skillet in the oven and roast until the chicken is cooked through. Approximately 20 - 25 minutes. An instant-read thermometer inserted in the thickest part should read 165℉. Remove the skillet from the oven and let rest for 5 minutes.
Spoon the relish over the chicken and serve.
Just Salt It, and enjoy!
My inspiration for this dish is from Bon Appétit Magazine May 2022. I made a few minor adjustments to my liking