Clean chicken and pat dry. Mix the lemon juice (reserving the lemon halves), minced garlic, chopped basil, and olive oil in a bowl, then rub evenly over the entire bird.
Carefully, lift the skin over the breasts and rub the mixture directly on the breast meat. Place the onion and garlic inside the cavity along with some extra basil leaves and the used lemon halves. Sprinkle the top of the bird with a little extra sea salt and freshly cracked pepper.
Place chicken on a roasting tray in a roasting pan. Place a meat thermometer in the thickest part of the thigh, be sure not to touch the bone.
Roast uncovered for 3½ - 4 hours until the meat thermometer reads 180 degrees. Side Note: I start basting my bird after 2 hours and repeat every ½ an hour. My chicken turns out sticky and slightly crispy. If you want crispy skin, don't baste for the last hour and turn the heat to 350 degrees for the few minutes of cooking.
Remove from the oven and let the bird rest for AT LEAST 10 minutes before carving. Enjoy!