The 21-year-old sealed the world champions` 3-1 win in Sochi with a second-half brace by heading home Joshua Kimmich`s cross, then drilled in a second to calm German nerves just after Vincent Aboubakar netted Cameroon`s consolation goal.
Russia, a record low 63rd in FIFA's world rankings, face Portugal on Wednesday and New Zealand play Mexico the same day.
The four-time World Footballer of the Year has helped Real win the Champions League three times and La Liga twice.
Madrid sports media is awash with headlines suggesting Ronaldo wants out of the Spanish champions, despite only signing a new contract through to 2021 in November.
Midfielder Eden Hazard tried to play down speculation that he is about to move away from Stamford Bridge by describing how settled he feels with his Chelsea "family".
World Cup holders Germany and the FIFA Confederations champions compete in the eight-team tournament which will put Russia`s ability to handle thousands of visiting and home fans under the spotlight.
It is 13-years since Wenger`s `Invincibles` won the last of his three Premier League titles and the club has just come through their worst season in two decades.
Since its inception in 1997, the Confederations Cup has been won four times by Brazil, twice by France and once by Mexico.
Russian President Vladimir Putin will attend the opener along with FIFA boss Gianni Infantino at Saint Petersburg's purpose-built World Cup 68,000-seater stadium.
Messi marries his childhood sweetheart Antonella Roccuzzo, 29, on June 30, a week after the player's 30th birthday, in Latin America's celebrity wedding of the decade.
Ronaldo, Portugal`s all-time leading scorer, is the latest in a long line of soccer players in Spain -- among them Barcelona`s Lionel Messi and Neymar -- to be caught up in cases over tax or transfers.
Only Portugal star striker Cristiano Ronaldo, Argentina`s Lionel Messi and Clint Dempsey of United States stand ahead of the 32-year-old Indian.
Brazilian international Oscar moved to Shanghai SIPG for 60 million euros ($67 million) as Chinese clubs splashed an unprecedented 388 million euros the January-February window.
The 22-year-old England international scored 10 goals in all competitions last season and believes that Guardiola can help him develop further.
With no Mueller or Gomez around, RB Leipzig`s Timo Werner, the Bundesliga`s top-scoring German forward last season with 21 goals, and Hoffenheim`s burly striker Sandro Wagner will have their chance to shine.