Apex domains cannot have CNAME records.
Question and response
Question
dig izzi.mx. NS
Answer
izzi.mx. 5 NS a12-66.akam.net.
izzi.mx. 5 NS a5-65.akam.net.
izzi.mx. 5 NS a1-229.akam.net.
izzi.mx. 5 NS a10-64.akam.net.
izzi.mx. 5 NS a16-65.akam.net.
izzi.mx. 5 NS a13-67.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0