Apex domains cannot have CNAME records.
Question and response
Question
dig acomma.com. NS
Answer
acomma.com. 2 NS ns3.wwi.as.
acomma.com. 2 NS ns2.locuples.com.
acomma.com. 2 NS ns.locuples.com.
acomma.com. 2 NS ns4.wwi.eu.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0