Apex domains cannot have CNAME records.
Question and response
Question
dig static.highway.a1.net. NS
Answer
static.highway.a1.net. 4 NS dns4.a1.net.
static.highway.a1.net. 4 NS dns5.a1.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0