The Reds were solid, if unspectacular, in overcoming the Portuguese side, and were indebted to two superb saves from Edwin van der Sar either side of Ronaldo’s goal.
In a game of few chances, the Dutch goalkeeper's brilliant first-half save from Liedson was the platform for United’s triumph, while Nani and substitute Louis Saha both came close to doubling their margin of victory.
Ronaldo’s goal was enough to notch United’s 100th victory in the Champions League, however, and further good news was provided by a sprightly 71-minute outing for Wayne Rooney.
The England striker made his first appearance since suffering a fractured foot against Reading, and showed no lack of fitness as he ploughed a lone furrow upfront.
The opening exchanges between the two sides were bossed largely by the hosts, who seemed eager to test van der Sar from long-range at any given opportunity.
Having already been called into action on several occasions, the big Dutchman kept United on level terms in breathtaking fashion just before the half-hour mark, denying Liedson with an astonishing fingertip save.
The Brazilian was picked out on the edge of the United box and, having fashioned space for a shot, curled an effort which was bound for the top corner until van der Sar hurled himself towards the ball and clawed it around the