Gac (Momordica cochinchinensis) is a spiny, melon-sized tropical fruit of Southeast Asia, native to Vietnam and across the region from southern China to northern Australia. Beneath its bright orange-red, soft-spined rind sit large seeds wrapped in a deep-crimson, oily aril — among the richest natural sources of carotenoids known, prized in Vietnam for festive red sticky rice (xôi gấc).