Apex domains cannot have CNAME records.
Question and response
Question
dig shopify.com. NS
Answer
shopify.com. 5 NS gold.foundationdns.com.
shopify.com. 5 NS gold.foundationdns.org.
shopify.com. 5 NS gold.foundationdns.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0