With top spot already confirmed for City heading into the final group stage match, manager Pep Guardiola made seven changes to the team, handing youngsters Cole Palmer and Lewis starting opportunities at the Etihad Stadium.
However, against the run of play, the hosts took the lead through Rafa Mir's header.
But shortly after the interval, 17-year-old Lewis was played through expertly by Julian Alvarez, before firing in at the near post to level to score to create Champions League history.
With just over 15 minutes remaining, Alvarez turned from provider to scorer, latching onto Kevin de Bruyne's sumptuous pass before going around the goalkeeper and slotting into the roof of the net.
The Argentine then returned to being provider, setting up Riyad Mahrez to add a superb third of the evening, curling the ball into the top right corner.
View the best images from the match via our gallery below.