BT RH 21a(3) :בסים {ונכ}<תב>שילא דבבלאיי ביומא רבא דמערבא‏ : the cooked dish of the Babylonians is tasty on the (fast) Day of Atonement of the land of Israel
See the entire entry for ywmˀ@rbˀ n.m. the Day of Atonement