Place the top oven rack in the center position and pre-heat the oven to 400°F. Zest one of the lemons with a Microplane and cut the rest of it into quarters. Set the zest and lemon aside.
Slice the remaining lemon into ¼-inch thick slices and arrange on the bottom of a large, oven-safe skillet, along with the sliced yellow onion. Set aside.
In a small bowl, combine 2 tablespoons of olive oil with the lemon zest, butter, garlic powder, onion powder, and Herbes de Provence. Season with salt and black pepper, to taste, and stir with a fork to create a paste.
Stuff the chicken with the quartered lemon and 1/3 of the rosemary sprigs. Secure the legs together with kitchen string.
Place the chicken on top of the onions and lemon in the skillet and gently massage 1-2 tablespoons of the lemon-butter mixture under the skin. Spread the remaining mixture all over the outside of the chicken in an even layer.
In a large glass bowl, toss the baby red potatoes with the remaining olive oil and fresh rosemary. Season with salt and black pepper, as desired.
Nestle the seasoned potatoes around the chicken before adding the chicken broth and whole peppercorns. Place the skillet in the preheated oven to roast for one hour.
After an hour, remove from oven and check for doneness by inserting an instant-read thermometer between the leg and breast, but not against the bone.
Note: Chicken should reach an internal temperature just below 165°F before removing from the oven. The temperature will rise several degrees as it rests.
Let the chicken rest for 5-10 minutes before carving. Serve immediately topped with some of the juices from the skillet and the roasted rosemary potatoes on the side. Enjoy!
