The Annunciation, probably.

The Annunciation, probably 1425/1430
tempera (and possibly oil glazes) on panel, 148.8 x 115.1 cm (58 9/16 x 45 5/16 in.)
Andrew W. Mellon Collection

Unfortunately, that "probably" is referred to the date, and is not part of the title. If it was, it would've been the best title for a painting i've seen today. Sounds very Duchamp to me!

More information on this painting here.