The best source to analyze the Persian perspective of the Mongol Empire during Mongol rule would be the Jāmiʿ al-tawārīkh.
Why? The Jāmiʿ al-tawārīkh, also known as the "Universal History," was a significant historical work written by the Persian historian Rashid al-Din in the early 14th century. It provides a comprehensive account of the history of the Mongols, among other topics, and includes insights into how Persian society viewed the Mongol rulers and their impact on the region. This work is particularly valuable because it was created during the period of Mongol rule in Persia and reflects the synthesis of Persian and Mongol cultures.
In contrast, the other options (art by Andris Rublev or Theophanes the Greek, and a letter by Kublai Khan) do not specifically focus on the Persian perspective or historical context of the Mongol Empire and would not offer as thorough an understanding as the Jāmiʿ al-tawārīkh.