Apex domains cannot have CNAME records.
Question and response
Question
dig cello-online.com. NS
Answer
cello-online.com. 4 NS ns-503.awsdns-62.com.
cello-online.com. 4 NS ns-1167.awsdns-17.org.
cello-online.com. 4 NS ns-828.awsdns-39.net.
cello-online.com. 4 NS ns-1395.awsdns-46.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0