Apex domains cannot have CNAME records.
Question and response
Question
dig att.net. NS
Answer
att.net. 5 NS ohcu.oh.mt.np.els-gms.att.net.
att.net. 5 NS macu.ma.mt.np.els-gms.att.net.
att.net. 5 NS wycu.wy.br.np.els-gms.att.net.
att.net. 5 NS orcu.or.br.np.els-gms.att.net.
Authority
The response has no authority records.
Additional
macu.ma.mt.np.els-gms.att.net. 5 A 99.99.99.130
ohcu.oh.mt.np.els-gms.att.net. 5 A 99.99.99.128
orcu.or.br.np.els-gms.att.net. 5 A 68.94.156.130
wycu.wy.br.np.els-gms.att.net. 5 A 68.94.156.128
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0