The 1493 papal bull associated with dividing the New World between Spain and Portugal was Inter Caetera. Issued by Pope Alexander VI on May 4, 1493, it assigned lands west and south of a demarcation line to the Catholic Monarchs Ferdinand of Aragon and Isabella of Castile.
The line was placed 100 leagues west and south of the Azores and Cape Verde Islands. Portugal objected because the arrangement favored Castile, and negotiations produced the Treaty of Tordesillas in 1494. That treaty moved the dividing line westward to 370 leagues west of the Cape Verde Islands, allowing Portugal to claim Brazil.
A common mix-up is to answer “Treaty of Tordesillas.” The treaty created the later diplomatic settlement, while Inter Caetera was the papal decree that first established the proposed division. There were also multiple 1493 papal bulls titled Inter Caetera, but the May 4 bull is the one normally meant in this trivia context.