Apex domains cannot have CNAME records.
Question and response
Question
dig tula.net. NS
Answer
tula.net. 1 NS nsd3.tula.net.
tula.net. 1 NS nsd2.tula.net.
Authority
The response has no authority records.
Additional
nsd2.tula.net. 1 A 212.12.11.43
nsd3.tula.net. 1 A 212.12.11.44
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0