Is it permissible to curse the companions either in prescence of others or in absence? I mean either publicly or privately. P.S. Im a new revert and would like to have detailed answer with references.

Salawat means prayer to Allah that bless prophet and his family
Curse is prayer to Allah to deprive the enemies of prophet and his family from His blessings and that is command of Allah in two consecutive aayat from Surah Ahzab ayah no 56,57