Apex domains cannot have CNAME records.
Question and response
Question
dig deterlab.net. NS
Answer
deterlab.net. 4 NS ns3.isi.edu.
deterlab.net. 4 NS nsdo.deterlab.net.
deterlab.net. 4 NS ns4.isi.edu.
deterlab.net. 4 NS ns2.deterlab.net.
deterlab.net. 4 NS ns2.isi.edu.
Authority
The response has no authority records.
Additional
ns2.isi.edu. 4 A 128.9.40.13
ns3.isi.edu. 4 A 128.9.49.6
ns4.isi.edu. 4 A 128.9.40.14
nsdo.deterlab.net. 4 A 209.38.117.213
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0