This relief is attributed to Donatello, although in an older text I found online the author is pretty skeptical:
"The Madonna in the Via Pietra Piana at Florence belongs to a different category. Here again the design is Donatellesque, but the face of the Madonna has a dull and vacant look; not only is it without the powerful modelling of the Pazzi or Siena reliefs, but it shows none of the sentiment for which those two Madonnas are so remarkable."
It is hard to photograph behind the dirty glass case, which usually has a terrible glare. The other day with a bit of overcast sky I managed to get this shot:
And here it is on Google Street View: