Apex domains cannot have CNAME records.
Question and response
Question
dig nts-online.net. NS
Answer
nts-online.net. 1 NS dns1.nts-online.net.
nts-online.net. 1 NS dnscache01.xfoneusa.net.
nts-online.net. 1 NS ns2.xfoneusa.net.
nts-online.net. 1 NS dnscache02.xfoneusa.net.
nts-online.net. 1 NS ns1.xfoneusa.net.
nts-online.net. 1 NS dns2.nts-online.net.
Authority
The response has no authority records.
Additional
dns1.nts-online.net. 1 A 216.167.161.35
dns2.nts-online.net. 1 A 216.167.161.36
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0