Apex domains cannot have CNAME records.
Question and response
Question
dig rsgsv.net. NS
Answer
rsgsv.net. 5 NS pdns177.ultradns.biz.
rsgsv.net. 5 NS pdns177.ultradns.com.
rsgsv.net. 5 NS pdns177.ultradns.net.
rsgsv.net. 5 NS pdns177.ultradns.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0