Preheat oven to 375 degrees Fahrenheit.
Chop parsley. Add to a small bowl with butter and pepper and stir to combine. Add in juice from one lemon and stir to combine.
Slice onion, chop potatoes, peel and chop carrots and cut lemons in half.
In a large soup pot, add sliced onions, potatoes, carrots and lemon.
With chicken breast down, add parsley lemon mixture inside and on top. Add in slices of lemon.
Put chicken on top of veggies and add cover.
Roast covered for 1 hour. Then roast for 30 more minutes uncovered.