Complex sentence: The first "auto da fé" took place in Seville in 1481, when six "conversos" (Jews forcibly converted to Christianity) were burnt at the stake.
Split into simpler sentences: The first "auto-da-fé" (Spanish, "act of faith") took place in Seville in 1481. During this time six "conversos" (Jews forcibly converted to Christianity) were burnt at the stake.