The 41-year-old striker made it 1-0 after just six minutes, making him the first player to score in six different World Cups.
Ronaldo also became the second oldest goalscorer in World Cup history - only beaten by Cameroon's Roger Milla, who was 42 during the 1994 championship in the United States.
Ronaldo also made it 3-0 with a goal largely created by his speed.
The period after his debut (a 1-1 draw against DR Congo) has been turbulent for the star. TV pundits called Ronaldo "sad" and teammate João Neves' girlfriend described him as "selfish" on Instagram.
"It's been a tough week, a dark week. It seemed like I had given up on football," Ronaldo said in a television interview immediately after the match.
"But I persevered as always, because I believe in hard work more than anything else."
The days leading up to the group final against Colombia (1:30 a.m. on Sunday) will now be calmer.
