Prestianni will now miss Wednesday's return leg at the Santiago Bernabeu, with Real Madrid holding a 1-0 lead from the first leg in Lisbon.
The Argentine covered his mouth with his shirt and insulted Vincius Jr during the first-leg clash, shortly after the Brazilian opened the scoring, but denied allegations from the forward and multiple other Real Madrid players that his insult was racist.
UEFA have stated that a longer suspension could be handed out, with the governing body's Ethics and Disciplinary Commission continuing their investigation.
"This is without prejudice to any ruling that the UEFA disciplinary bodies may subsequently make following the conclusion of the ongoing investigation and its respective submission to the UEFA disciplinary bodies," a statement regarding the provisional ban reads.
Benfica have defended their player since the incident took place and have now confirmed that they will appeal the ruling.
“The club regrets being deprived of the player while the process is still under investigation and will appeal this Uefa decision, even if the applicable timelines are unlikely to have any practical effect on the second leg of the Champions League playoff," the club said.
“Benfica also reaffirms its unwavering commitment to combating all forms of racism and discrimination - values that are part of its historical identity and reflected in its daily actions, its global community, the work of the Benfica Foundation, and major figures in the club’s history, such as Eusebio.”
Referee Francois Letexier halted the first leg after activating FIFA's anti-racism protocols. Footage appeared to show Real forward Kylian Mbappe confronting Prestianni and calling him "a bloody racist", while images from the broadcast seemed to show Benfica fans imitating a monkey.
Prestianni denied the allegation, saying Vinicius "misunderstood what he thinks he heard". Mbappe told reporters he heard Prestianni direct the same racist remark at Vinicius several times, an allegation also made by Real's French midfielder Aurelien Tchouameni.
Mbappe said he had been prepared to leave the pitch but was persuaded by Vinicius to continue playing.
"We cannot accept that there is a player in Europe's top football competition who behaves like this. This guy (Prestianni) doesn't deserve to play in the Champions League anymore," Mbappe told reporters.
Vinicius later posted a statement on social media voicing his frustration.
"Racists are, above all, cowards. They need to cover their mouth with their shirt to show how weak they are. But they have the protection of others who, theoretically, have an obligation to punish them. Nothing that happened today is new in my life or my family's life," Vinicius wrote.
Anti-discriminatory body Kick It Out said focusing on Vinicius' goal celebration instead of acknowledging the report was a "form of gaslighting" after Benfica coach Jose Mourinho said he thought Vinicius had incited the crowd.
"This approach not only harms the individual affected but also sends the wrong message to others around the world who may have experienced similar situations," Kick It Out said.
Mourinho will not be on the bench for the second leg after receiving a red card for complaining in the first game.
