Preheat outdoor grill to medium heat. Place chicken breast-side-down on cutting board. Remove backbone by cutting along both sides using a pair of sharp kitchen shears. Turn chicken skin-side-up then lay flat on cutting board. Press it firmly against the board to flatten the chicken.

Pat chicken dry then rub skin side with olive oil, making sure to rub oil into all of the creases. Season generously on both sides with garlic powder, salt and pepper.

Place chicken skin-side-down on grill and allow to cook undisturbed for 15–18 minutes until the skin is crispy, golden and well-marked. Turn chicken and continue grilling until the internal temperature in thickest part of thigh registers 150 degrees on a meat thermometer—about 20–30 minutes, depending on size of chicken.

Remove chicken from grill then cover with foil. Allow chicken to rest, covered, for at least 10 minutes. Meanwhile, place lemon halves cut-side-down on grill and cook until they achieve grill marks and are well-caramelized.

Carve chicken into pieces and serve hot with grilled lemon for squeezing.