Apex domains cannot have CNAME records.
Question and response
Question
dig sfr.net. NS
Answer
sfr.net. 5 NS nspri01.dns.sfr.net.
sfr.net. 5 NS nspri00.dns.sfr.net.
Authority
The response has no authority records.
Additional
nspri00.dns.sfr.net. 5 A 109.0.66.6
nspri01.dns.sfr.net. 5 A 109.0.66.16
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0