Answer
The answer is "Axur, re d'Ormus", an opera seria in three acts composed by Antonio Salieri. It premiered on January 8, 1787, at the Burgtheater in Vienna. The libretto, by Lorenzo Da Ponte, is based on the French play "Tarare" by Beaumarchais. The opera tells the story of Axur, King of Ormus, who is overthrown by his vizier, Atar.