Heat oven to 350° F.
In a bowl, use a fork or wooden spoon to combine 8 tablespoons of the butter, the molasses, salt, pepper, and lemon juice; set aside.
Remove the turkey giblets and discard or reserve for another use. Rinse the turkey under cool running water. Pat completely dry with paper towels. Place on a rack in a roasting pan. Using your fingers, carefully spread the butter mixture evenly under the skin, reaching in as far as possible without ripping it. Place any remaining butter mixture in the cavity. Rub the remaining 2 tablespoons of butter on top of the skin. Add about 1 cup of water to the pan. Roast, uncovered, until browned, about 45 minutes. Cover loosely with a large sheet of foil. Continue to roast until a thermometer inserted in a thigh registers 180° F, 2 1/2 to 3 hours total, depending on the size of the turkey. Let stand, covered, for at least 30 minutes before slicing.
Tip: The molasses butter gives the turkey a rich flavor and a burnished color. No gravy required.