Which opera premiered first, Julietta or La favorite?
Julietta:  A libretto in Czech was later prepared for its 1938 premiere, and it has become widely considered as Martinů's masterpiece. La favorite: La Favorite (The Favourite, sometimes referred to by its Italian title: La favorita) is a grand opera in four acts by Gaetano Donizetti to a French-language libretto by Alphonse Royer and Gustave Vaëz, based on the play "Le comte de Comminges" by Baculard d'Arnaud. La favorite:  It premiered on December 2, 1840 at the Académie Royale de Musique (Salle Le Peletier) in Paris, France.
La Favorite