Place turnips in a large saucepan and cover with water. Bring to a boil. Reduce heat; cover and cook for 15 minutes or until tender and drain. Transfer turnips to a bowl and mash. Add the egg, sugar, butter and salt.
Transfer to a greased 1-qt. baking dish; sprinkle with cinnamon. Cover and bake at 350° for 20-25 minutes or until a thermometer reads 160°.