Toss the onion with a little olive oil in a small roasting pan. Pour the water into the pan. Place the chicken on top and sprinkle the inside of the cavity with about 1 teaspoons of the rub. Place the lemons and rosemary sprigs inside the chicken.
Place 2 tablespoons of butter under the skin of the breast. Rub the chicken all over with the olive oil and then rub with remaining Louisanna Creole Rub & Seasoning. Tuck the remaining butter around the legs of the chicken.
Roast for 1 ¼ to 1-½ hours or until the juices run clear when you cut between the leg and the thigh. You want the tempature to be about 155-160 degrees. Cover with foil and let sit for 15-20 minutes. The temperture will rise 5-10 degrees after cooking. You want the temperture to reach 165 degrees. Add ½ cup more water half way through the cooking time if the onions are starting to burn.