In 1921 he returned to Porto with his wife. At that time Barros Basto realized that there were fewer than twenty Ashkenazi Jews living in the city. As there wasn’t a synagogue in Porto these Jews were not organized and had to travel to Lisbon for religious purposes whenever necessary. Upon learning that reality he began to think about building a synagogue and took initiative in 1923, by officially registering the Jewish Community of the Porto and the Israelite Theological Center in the City Council of Porto. The current building of the synagogue was built years later but the community was organized and rented a house on the street Elias Garcia, which started to function as a synagogue. As time went on, more and more people started to appear in the synagogue. They said they were descendants of Jews forced to convert in the 15th century and claimed to maintain alive yet some Jewish practices and rituals, in the secrecy of their homes. These people, the crypto-Jews, began to participate in religious services. In 1927, he founded and directed the Portuguese Jewish Newspaper called Ha-Lapid. The claims of the crypto-Jews were proved true by Barros Basto and the committee of London, who found that they did not lie about their origins since they proved to still keep prayers to Hashem and respect the Sabbath as their ancestors. It should also be noted that on the Act n. º 68 Directorate (Maâmad) of the Jewish Community of Porto it was written that anyone who could "absolutely prove their Jewish origin." would be admitted into the congregation. This occurrence sparked Barros Basto’s interest, who therefore, decided to visit frequently the villages and towns of the Trás os Montes and Beiras regions, looking for more people interested in returning to Judaism. This measure gained the attention of some people, especially some Jewish communities, as is the case of the Community of Portuguese Jews in London, who created the "Portuguese Marranos Committee", an organization dedicated to help people who wanted to return to Judaism. With the change of regime in the 1930s, Barros Basto was associated with the opposition, and was soon being chased by the army. He started to be placed in locations farther away from Porto, in an attempt to push him away from the Synagogue and the Community. In 1937, Barros Basto was adjudicated by the Disciplinary Board of the Army and was dismissed from the institution for allegedly participating in circumcision ceremonies (in Hebrew, brit milah) of the students of the Israelite Theological Institute of Porto, which the Council considered "immoral" act, which is actually a fundamental practice for the Jewish people.