Apex domains cannot have CNAME records.
Question and response
Question
dig uservoice.com. NS
Answer
uservoice.com. 5 NS ns2.uservoice.com.
uservoice.com. 5 NS ns1.uservoice.com.
Authority
The response has no authority records.
Additional
ns1.uservoice.com. 5 A 173.245.58.34
ns2.uservoice.com. 5 A 173.245.59.14
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0