Apex domains cannot have CNAME records.
Question and response
Question
dig static.as29550.net. NS
Answer
static.as29550.net. 5 NS a.ns.as29550.net.
static.as29550.net. 5 NS c.ns.as29550.net.
static.as29550.net. 5 NS b.ns.as29550.net.
Authority
The response has no authority records.
Additional
a.ns.as29550.net. 5 A 217.112.87.148
b.ns.as29550.net. 5 A 85.234.157.254
c.ns.as29550.net. 5 A 213.229.79.255
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0