Apex domains cannot have CNAME records.
Question and response
Question
dig postesdelsureste.com. NS
Answer
postesdelsureste.com. 5 NS ns2.postesdelsureste.com.
postesdelsureste.com. 5 NS ns1.postesdelsureste.com.
Authority
The response has no authority records.
Additional
ns1.postesdelsureste.com. 5 A 170.130.204.210
ns2.postesdelsureste.com. 5 A 50.3.109.110
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0