Apex domains cannot have CNAME records.
Question and response
Question
dig salesmanago.mx. NS
Answer
salesmanago.mx. 4 NS tani.ns.cloudflare.com.
salesmanago.mx. 4 NS lynn.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0