Salomon wrote pioneering work in Sephardic history and Inquisition studies. Besides his scholarly articles, his most important contributions were his annotated translations of important works by Amsterdam Jews. Early in his career, Salomon published and translated to English a unique family history written by the Portuguese-Jewish merchant Isaac de Pinto, who fled Antwerp for the Dutch Republic in 1646. A connoisseur of archival documents as well as manuscripts, Salomon published and analyzed documents preserved in Portugal’s national archives in his volume Os primeiros portugueses de Amesterdão, which illuminated the earliest years of ex-converso settlement in Amsterdam.[2] In another major contribution, Salomon published in 1988 an annotated edition of a lengthy and fascinating manuscript by the learned Amsterdam rabbi Saul Levi Mortera, Tratado da verdade da lei de Moisés, in which the author articulated a Jewish position on Calvinism (liberally citing passages from Calvin’s Institutes).
Of Salomon's literary discoveries, one stands out in particular. Jointly with his colleagues Adri Offenberg and Harm den Boer, he undertook systematic efforts to retrieve the lengthy, long-lost work Exame das tradições phariseas (Examination of Pharisaic Tradition), in which Uriel da Costa had attacked rabbinic Judaism and the doctrine of the immortality of the soul. This work, printed in Amsterdam in 1623, was soon thereafter banned and destroyed. Scholars had searched in vain for a surviving copy until Salomon found one in the Royal Library in Copenhagen in 1989. He and I.S.D. Sassoon published the text in 1993 in a facsimile edition with an English translation. Da Costa’s recovered treatise is now essential reading for the study of early challenges to rabbinic authority among Amsterdam’s Portuguese Jews.
In 2014, Salomon published the extensive confidential memoirs of the Portuguese Inquisitor António Ribeiro de Abreu, who in 1738 and 1743 defended his institution against the critique of the jesuit António Vieira. This text, which offers a unique insight into the workings of the Holy Office, appeared in the original Portuguese under the title Queimar Vieira em estátua (Burning Vieira in Effigy).