Martirena opened the scoring in the 15th minute and Martinez added a goal five minutes later to give "La Academia" their first international title since 1988 when they won the now defunct Supercopa Sudamericana.
"Maravilla" Martinez scored 10 goals in 13 matches and finished as the top scorer in the competition.
"We suffered until the last minute, but to be able to win a cup after so many years is a blessing," Martinez said. "It's historic, it was a long time without being able to raise an international cup, we have a poor year in the league, but we were able to give the fans this satisfaction."
Roger Martinez sealed the victory with a goal in the 90th.
Kaio Jorge scored in the 52nd for Cruzeiro.
Racing, a team based in the city of Avellaneda, took the lead when Martirena, a Uruguayan right-back, sent in what appeared to be a cross from the right but the looping ball went over Cruzeiro goalkeeper Cassio and into the far corner of the net.Â
Martinez doubled the lead with a shot from five metres.
Saturday's final was played in Estadio General Pablo Rojas in Asuncion, Paraguay, where most of the 45,000 fans were supporting Racing.
Copa Sudamericana is the second most prestigious club competition in South America behind the Copa Libertadores, and its first edition was in 2002.
Racing are the first Argentinian team to win the competition since 2020 when Defensa y Justicia beat Lanus. The last two competitions were won by Ecuadorian teams.
Brazilian teams Atletico Mineiro and Botafogo will play next weekend in the Copa Libertadores final in Buenos Aires, Argentina.
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