Apex domains cannot have CNAME records.
Question and response
Question
dig alexmuriuki.com. NS
Answer
alexmuriuki.com. 5 NS ns2.alexmuriuki.com.
alexmuriuki.com. 5 NS ns1.alexmuriuki.com.
Authority
The response has no authority records.
Additional
ns1.alexmuriuki.com. 5 A 144.217.79.195
ns2.alexmuriuki.com. 5 A 51.79.11.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0