Unfortunely, all my tango recordings are by groups.
I do recommend Daniel Barenboim's
Mi Buenos Aires Querido (Tangos Among Friends) though. Most of the songs are trios (piano, bandoneon, bass), but there are 3 solo piano pieces. On of the solo pieces is Astor Piazzolla's
Adios Nonino, the only tango piece that I regularly here played on solo piano.
If you have access to the Label Bleu catalogue, you might want to look for
Hernan Lugano. He has recorded a couple of solo tango records. I haven't heard his work, most of Label Bleu's artists are worth hearing.
Now that you've mentioned it, I'm going to look for some solo piano tango.