Assenzio and Osteria del Sole are run by the same folks. Both are excellent and reasonably priced. The menus feature Ligurian dishes as well as Sardinian, as the partners are from those two regions.
I don't know if it's particularly Sardinian, but I know they have had some Sardinian specials and even a Sardinian wine at I Pisticci in Morningside Heights on LaSalle. One of the bartenders there is Sardinian.