Place cubed rutabaga in large saucepan with enough water to cover. Bring water to boil, cover and reduce heat. Simmer 30 minutes or until rutabaga is tender when pierced with a fork. Drain water.
Mash rutabaga and butter with the Masher Attachment until chunky with some small cubes. Add salt and pepper; stir to blend.
TIP: Make one day ahead and store covered in the refrigerator. Reheat before serving.