1. On a lightly floured surface, roll the dough into a 12-by-14-inch rectangle with the longer side facing you.
2. Spread with the softened butter, leaving a 1/2-inch border on the far long edge. Mix the sugar and cinnamon; sprinkle over the butter.
3. Brush the unbuttered far edge with water. Roll the dough away from you into a tight cylinder and press on the long edge to seal.
4. Cut the cylinder with a sharp knife to make 6 equal-size buns.