Apex domains cannot have CNAME records.
Question and response
Question
dig saludcoop.coop. NS
Answer
saludcoop.coop. 5 NS ns6.mysite.coop.
saludcoop.coop. 5 NS ns7.mysite.coop.
saludcoop.coop. 5 NS ns8.mysite.coop.
saludcoop.coop. 5 NS ns5.mysite.coop.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0