Tsitsipas, 20, claimed a third career crown after lifting trophies in Stockholm last October and Marseille in February and is expected to rise to nine in the world on Monday.
Uruguay's Cuevas, 33, made the final as a lucky loser having originally lost in qualifying last weekend.
"You really have to fight hard and give your soul out on the court. This title means a lot to me," said Tsitsipas.
"It's on clay, it's one of my preferred surfaces. It's nice to have completed the clay-hard court title sweep that I've been fighting for. Next is grass, or maybe even more clay-court titles this year, that would be wonderful."
On Saturday, Sakkari had claimed her maiden WTA title with a 2-6, 6-4, 6-1 win over Britain's Johanna Konta in the Rabat clay court final.