Apex domains cannot have CNAME records.
Question and response
Question
dig dfw.wordpress.com. NS
Answer
dfw.wordpress.com. 2 NS ns2.wordpress.com.
dfw.wordpress.com. 2 NS ns4.wordpress.com.
dfw.wordpress.com. 2 NS ns1.wordpress.com.
dfw.wordpress.com. 2 NS ns3.wordpress.com.
Authority
The response has no authority records.
Additional
ns1.wordpress.com. 2 A 198.181.116.9
ns2.wordpress.com. 2 A 198.181.117.9
ns3.wordpress.com. 2 A 192.0.74.9
ns4.wordpress.com. 2 A 192.0.75.9
ns1.wordpress.com. 2 AAAA 2a04:fa87:ffff:0:0:0:c6b5:7409
ns2.wordpress.com. 2 AAAA 2a04:fa87:ffff:0:0:0:c6b5:7509
ns3.wordpress.com. 2 AAAA 2620:115:c00f:0:0:0:c000:4a09
ns4.wordpress.com. 2 AAAA 2620:115:c00f:0:0:0:c000:4b09
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0