Involved in anthocyanin biosynthesis by catalyzing the galactosylation of cyanidin (PubMed:21175894, PubMed:29057484, PubMed:30912865). Required for the accumulation of anthocyanin in red-fleshed kiwifruit varieties (PubMed:21175894, PubMed:29057484, PubMed:30912865). Seems to be the key enzyme regulating the accumulation of anthocyanin in red-fleshed kiwi fruits (PubMed:21175894, PubMed:29057484, PubMed:30912865). cyanidin + UDP-alpha-D-galactose = cyanidin 3-O-beta-D-galactoside + H(+) + UDP Pigment biosynthesis; anthocyanin biosynthesis. Expressed at low levels in stems and leaves (PubMed:25143057). Expressed in ovaries (PubMed:21175894). Expressed in the inner and outer pericarps of developing fruit at 20 days after flowering (DAF) (PubMed:21175894). Expressed only in the inner pericarp from 86 to 126 DAF (PubMed:21175894). Belongs to the UDP-glycosyltransferase family.