존맛탱

Extremely delicious — way beyond just tasty. From 존나 (intensifier) + 맛 (taste) + 탱, where 탱 traces back to 탱구, a nickname given to SNSD's Taeyeon by fans. 탱 survived purely as a cute emphasis sound with no literal meaning.

존 = intensifier (shortened from '존'나)

맛 = taste, flavor (맛)

탱 = cute emphasis sound (originally from Taeyeon's fan nickname '탱'구)