The 20-year-old fired into an unguarded net after coolly rounding goalkeeper Diego Cavalieri following a counterattack at the Couto Pereira stadium Saturday, reported Xinhua.
The victory lifted the hosts to 14th in the standings while Fluminense dropped to fifth.
Meanwhile Cleo struck either side of halftime as Atletico Paranaense beat 10-man Botafogo 2-0.
Botafogo defender Julio Cesar was sent off in the 67th minute for a crude challenge on Atletico midfielder Deivid.
In Saturday’s only other match, Atletico Mineiro won 2-0 at Palmeiras.