Preheat oven to 400ºF.
Rinse sweet potatoes, pat dry with paper towels, and cut into thin wedges. Place the sweet potato wedges, whole peppers and 2/3 of the stock in a large oven-safe skillet.
Cover the skillet with aluminum foil and place on the middle rack in the oven and bake for about 10 minutes.
While the vegetables are cooking, in a resealable plastic bag add whole chicken breasts, garlic, Italian seasoning, Sicilian spice, salt, and oil. Let the chicken marinate for about 10 minutes.
Reduce the oven temperature to 350ºF. Remove the skillet from the oven. Using tongs push the peppers and potatoes to the sides of the skillet. Use the same tongs to wedge the marinated chicken breasts down onto the surface of the skillet.
Pour tomatoes and the remaining 1/3 of stock over the skillet. Arrange vegetables evenly around and over the chicken.
Cover the skillet with aluminum foil, place on the middle rack in the oven and bake for 50 minutes, until the chicken is cooked through with an internal temperature of 165 ºF.
Distribute the chicken, peppers, and tomatoes evenly over each plate to serve.