4 lb whole chicken cut into 6 to eight pieces, keeping on the skin and bones
1/4 cup salt
1 teaspoon lemon zest
1/4 cup loosely packed rosemary leaves
1 tablespoon olive oil
4 tablespoons butter
1 medium onion, chopped fine
2 garlic cloves, minced
4 tablespoons flour
1 cup chicken broth
Zest and juice of 2 lemons (1/3 cup juice and 1 tablespoon zest)
1 tablespoon rosemary leaves, chopped
Brine the chicken by placing the pieces in a large zip close bag. Mix the salt, lemon zest and rosemary leaves with 1 quart of water and stir until salt is dissolved. Pour over chicken and seal well. Place in the refrigerator for at least 1 hour and as many as three.
Preheat the oven to 450 degrees F.
Remove chicken from brine, picking off any rosemary leaves and pat dry. Heat the oil in a cast iron skillet until smoking hot. Place chicken in the pan, skin side down. Cook until browned about 8 to 10 minutes. Remove breasts from skillet and turn over the rest of the chicken and cook the second side for 5 minutes more. Remove chicken from pan.
Pour out the fat from the pan. Toss in the butter and melt. Add in the onions and cook until translucent, about 5 minutes. Add in the garlic and sauté for a minute more. Sprinkle on the flour and cook until the roux becomes the color of peanut butter, 3 to 5 minutes. Slowly whisk in the chicken broth and the lemon juice. Continue to stir until the sauce is smooth and it comes to a simmer.
Pour in any juices from the chicken and then add the chicken back to the pan, skin side up. Place in the preheated oven and bake for 30 minutes. While the chicken cooks, stir together the lemon zest and rosemary leaves.
Remove the pan from the oven and turn on the broiler to high. Place the chicken on a baking sheet (I used the one I finished the potatoes on) and broil for 5 to 10 minutes, until the skin is crisp and dark brown but not burned and the breasts register 160 degrees F and thighs and drumsticks register 175 degrees F. You might need to rotate the pan during the broil.
While the chicken is broiling, sprinkle half of the rosemary lemon zest into the sauce and stir to combine.
Remove the chicken from the broiler and rest for 5 minutes before plating. Ladle gravy over each piece of chicken and sprinkle remaining rosemary lemon zest over the top of each plate and serve.