Apex domains cannot have CNAME records.
Question and response
Question
dig operadors.cat. NS
Answer
operadors.cat. 5 NS ns1.operadors.cat.
operadors.cat. 5 NS ns2.operadors.cat.
Authority
The response has no authority records.
Additional
ns1.operadors.cat. 5 A 185.242.248.3
ns2.operadors.cat. 5 A 185.242.248.4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0