Catalyzes the 3-beta-hydroxylation of 2S-flavanones to 2R,3R-dihydroflavonols which are intermediates in the biosynthesis of flavonols, anthocyanidins, catechins and proanthocyanidins in plants (PubMed:18413994, PubMed:18726614). Converts (2S)-eriodictyol to (+)-taxifolin and (2S)-naringenin to (+)-(2R/3R)-dihydrokaempferol in vitro (PubMed:18413994). 2-oxoglutarate + a (2S)-flavan-4-one + O2 = a (2R,3R)-dihydroflavonol + CO2 + succinate Binds 1 Fe(2+) ion per subunit. Secondary metabolite biosynthesis; flavonoid biosynthesis. Expressed at very low levels in roots, leaves, stems and seeds. Induced by light. Belongs to the iron/ascorbate-dependent oxidoreductase family.