When a Sonata simply goes by COMPOSER-NAME-Sonata it signals something:

The Sonata in A major for Violin and Piano by César Franck [or commonly just referred to as the Frank Sonata] is one of his best-known compositions, and is considered one of the finest sonatas for violin and piano ever written. It is an amalgam of his rich native harmonic language with the Classical traditions he valued highly, held together in a cyclic framework. Wikipedia

And it was a wedding gift… (who wouldn’t want a gift like this?)

The Violin Sonata in A was written in 1886, when César Franck was 63, as a wedding present for the 28-year-old violinist Eugène Ysaÿe.

Franck was not present when Ysaÿe married, but on the morning of the wedding, on 26 September 1886 in Arlon, their mutual friend Charles Bordes presented the work as Franck’s gift to Ysaÿe and his bride Louise Bourdeau de Courtrai. After a hurried rehearsal, Ysaÿe and Bordes’ sister-in-law, the pianist Marie-Léontine Bordes-Pène, played the Sonata to the other wedding guests.

Hear an amazing version performed by Jacqueline Du Pré & Daniel Barenboim, with the piece transcribed for cello: