The Argentine slumped to the court in joy after winning the last five games of the final, capping off a life-changing week.
An all-Spanish affair between Alejandro Davidovich-Fokina and Bernabe Zapata Miralles was an excellent contest of high-quality tennis.
The most eye-catching fixture of all on the opening day was the one between Dusan Lajovic and fifth seed Frances Tiafoe.
The ATP 250 competition is held in Cascais, Portugal, and is one of the many clay-court tournaments ahead of Roland Garros.