First spatchcock the chicken by placing the chicken breast side down on a work surface. Using kitchen shears cut along the backbone of the chicken starting at the bottom. Cut the other side and save the backbone to make stock. Flip the chicken over and using your palm press firmly on the breastbone to flatten the chicken. Wash the chicken thoroughly and dry it with a paper towel.
In a food processor add the cilantro, green chilies, garlic, lemon juice, ground cumin, and a pinch of salt. Blend till smooth paste. Keep aside.
Rub the chicken with 1 tbsp. oil and season generously with a salt and pepper all over, inside and out. Place the chicken skin side down in a tight container so that marinade will stick to the chicken. Pour half the green masala over the chicken and rub it all over the chicken. Flip the chicken over skin side up and repeat. Cover with plastic and let the chicken marinate for 12 hours.
Pre- heat oven to 400 degrees. Remove the chicken from the fridge and let it sit out for at least 10 minutes. Brush the center of a large rimmed baking sheet with the remaining 1 tablespoon of oil. Place the chicken skin side up on the baking sheet. Roast chicken for 45 minutes or until a thermometer inserted into thickest part of the breast reaches 165 degrees. It’s important to watch your chicken because everyone’s ovens are different so your bird might cook faster than mine.
You want the chicken to be brown and crispy. Remove the chicken from the oven and let it rest for 10 minutes. Carve the chicken into pieces and squeeze more lemon juice over the chicken.