_spf.uba.ar has no CNAME records.
Question and response
Question
dig _spf.uba.ar. NS
Answer
The response has no answer records.
Authority
uba.ar. 5345 SOA ns1.uba.ar. oper.ccc.uba.ar. 2025121100 600 1200 1296000 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0