Apex domains cannot have CNAME records.
Question and response
Question
dig ig.com.br. NS
Answer
ig.com.br. 5 NS ns-1766.awsdns-28.co.uk.
ig.com.br. 5 NS ns-798.awsdns-35.net.
ig.com.br. 5 NS ns-485.awsdns-60.com.
ig.com.br. 5 NS ns-1118.awsdns-11.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0