Apex domains cannot have CNAME records.
Question and response
Question
dig sante.santnet.com. NS
Answer
sante.santnet.com. 4 NS tigre.santnet.com.
sante.santnet.com. 4 NS puma.santnet.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0