Apex domains cannot have CNAME records.
Question and response
Question
dig ptero12mail.com. NS
Answer
ptero12mail.com. 3 NS ns3.limautils.com.
ptero12mail.com. 3 NS ns1.limautils.com.
ptero12mail.com. 3 NS ns2.limautils.com.
Authority
The response has no authority records.
Additional
ns1.limautils.com. 3 A 173.255.198.80
ns2.limautils.com. 3 A 168.235.79.211
ns3.limautils.com. 3 A 139.162.132.58
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0