Preheat your grill to a steady medium heat, about 350-400°F (175-200°C), and lightly grease the grates.
In a small bowl, whisk together the melted butter, lemon juice, lemon zest, oregano, paprika, onion powder, and garlic powder.
Season generously with salt and pepper to create a rich flavor paste.
Place the chicken on a large cutting board, breast-side down.
Using sturdy kitchen shears, carefully cut along both sides of the backbone to remove it completely. (You can save the backbone to make a delicious chicken stock later!)
Flip the chicken over and open it like a book. Press down firmly on the breastbone with the heel of your hand until you hear a crack and the chicken lies flat.
Pat the entire chicken dry with paper towels for extra crispy skin.
Generously coat the entire chicken with the butter and spice mixture. Be sure to get it into every nook and cranny, and if you're feeling adventurous, loosen the skin over the breasts and thighs to rub some of the mixture directly on the meat.
Place the chicken on the grill, skin-side up. Close the lid and cook for 20-25 minutes. Carefully flip the chicken and grill for another 15-20 minutes, or until the skin is golden and crisp and an instant-read thermometer inserted into the thickest part of the thigh registers 165°F (74°C).
Remove the chicken from the grill and transfer it to a clean cutting board.
Let it rest for at least 10 minutes before carving. This crucial step allows the juices to redistribute, ensuring a moist and tender result.
Resting the chicken after grilling is non-negotiable. Skipping this step will result in a dry bird, as all the delicious juices will run out onto your cutting board instead of staying in the meat.