Apex domains cannot have CNAME records.
Question and response
Question
dig tds.net. NS
Answer
tds.net. 5 NS d.dns.tds.net.
tds.net. 5 NS b.dns.tds.net.
tds.net. 5 NS c.dns.tds.net.
tds.net. 5 NS a.dns.tds.net.
tds.net. 5 NS e.dns.tds.net.
tds.net. 5 NS f.dns.tds.net.
tds.net. 5 NS ns.tds.net.
Authority
The response has no authority records.
Additional
a.dns.tds.net. 5 A 216.165.129.164
b.dns.tds.net. 5 A 64.50.232.116
c.dns.tds.net. 5 A 64.50.230.116
d.dns.tds.net. 5 A 204.246.0.9
e.dns.tds.net. 5 A 134.215.200.120
f.dns.tds.net. 5 A 66.173.0.4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0