Fill a large pot with cold water and a generous amount of salt. Bring the water to a boil and add the shell macaroni.
Boil until the macaroni is almost cooked through, but not quite, about 2 minutes less than the directed cook time on the box. Drain and return to the pan.
Add the tomato juice to the shell macaroni along with the salt and pepper. Bring it back to a boil and then let it simmer until the macaroni has softened to your liking and the tomato juice has thickened, about 7 minutes.
Stir in the butter, if desired, just before serving.
