- In a small bowl, combine oil, sugar, salt, pepper, paprika, cumin, coriander, onion powder, garlic powder, and ancho chili powder.
- To butterfly the chicken, with the breast side down, remove the backbone by cutting along either side with kitchen shears. Then use a sharp knife to score the breastbone down the center. Turn chicken over so that the breast side is up. Using the palm of your hand, press down hard to flatten the chicken. Alternatively, when purchasing your chicken, ask your butcher to butterfly it for you.
- Rub chicken on both sides with seasoning mixture.
- To grill, preheat a gas or charcoal grill to 350°F. Place chicken skin side down directly on oiled grate. Place a sheet of foil over chicken and weigh down with a heavy skillet or foil covered bricks. Close lid and cook 12 minutes.
- Using potholders, carefully lift weights off chicken, remove and discard foil, and flip chicken using 2 sets of tongs or metal spatulas. Place a fresh sheet of foil over chicken and replace heavy skillet or bricks. Cook until internal temperature reaches at least 170°F for dark meat and 155°F for breast meat, 30-40 minutes.
- To use an oven, preheat to 425°F, and heat a heavy skillet, such as cast-iron, over medium heat. Place chicken skin side down in skillet. Lay a sheet of foil over chicken and weight with another skillet or bricks covered in foil. Let cook on stovetop for 3-5 minutes or until the skin is browned. Remove skillet or bricks and foil, flip chicken breast side up with tongs, then tent with foil, place skillet in oven, and cook until internal temperature reaches at least 170°F for dark meat and 155°F for breast meat, 35-40
- Let chicken rest 10 minutes before cutting into pieces. The temperature will rise 5-10 degrees during the rest period.
- While chicken is resting, make the chimichurri. In a small bowl, stir together parsley, olive oil, lime juice, onion, jalapeño, garlic, and salt.
- Cut chicken into 8 pieces and serve drizzled with chimichurri.