Preheat your oven to 450°F (232°C) °F.
Prepare the Chicken: Remove the giblets from the cavity, trim any excess fat or leftover feathers, and pat the chicken dry with paper towels. Using a small, sharp knife, make approximately 12 small slits across the chicken. Insert the garlic pieces into each slit, ensuring they are fully embedded.
Prepare the Marinade: In a medium mixing bowl, whisk together ¼ cup olive oil, ¼ cup chicken broth, ¼ cup lemon juice, ½ teaspoon crushed red pepper flakes, and 1 teaspoon EACH: dried rosemary, oregano and thyme. Set aside.
Season & Stuff the Chicken: Place the chicken breast-side up in a roasting pan or skillet. Generously season with 2 teaspoons salt and ½ teaspoon ground black pepper.
Stuff the chicken cavity with 1 whole head of garlic (halved) and ½ lemon. Truss the chicken by tying the legs together with kitchen string to ensure even roasting.
Roast the Chicken: Pour the olive oil-lemon mixture over the chicken, ensuring it is well coated. Arrange 1 red onion (quartered) around the chicken and lightly season them with salt.
Place the roasting pan in the oven and cook until the chicken develops a deep golden-brown color, about 15-20 minutes. Once browned, reduce the oven temperature to 350°F (177°C) and continue roasting for 40-50 minutes, basting occasionally, until the internal temperature reaches 165°F (74°C). The juices should run clear when pierced with a knife.
Remove the chicken from the oven and let it rest for 10 minutes to allow the juices to redistribute evenly.
Serve warm, drizzled with the pan juices, alongside your favorite sides. Enjoy!