Apex domains cannot have CNAME records.
Question and response
Question
dig lumen.tech. NS
Answer
lumen.tech. 4 NS authns2.lumen.tech.
lumen.tech. 4 NS authns1.lumen.tech.
lumen.tech. 4 NS authns1.qwest.net.
lumen.tech. 4 NS authns2.qwest.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0