Do CNAME records result in a second DNS lookup?

The 2 records are returned together in the same request. You can find that out via the following command

dig +trace www.foo.com

For example my domain photoblog.com has a cname for www so the last 2 requests from photoblog's name server to me look like

photoblog.com.      172800  IN  NS  ns1.photoblog.com.
photoblog.com.      172800  IN  NS  ns2.photoblog.com.
;; Received 103 bytes from 192.43.172.30#53(i.gtld-servers.net) in 196 ms

www.photoblog.com.  600 IN  CNAME   photoblog.com.
photoblog.com.      600 IN  A   74.52.128.18
photoblog.com.      60  IN  NS  ns2.photoblog.com.
photoblog.com.      60  IN  NS  ns1.photoblog.com.
;; Received 133 bytes from 74.52.128.18#53(ns2.photoblog.com) in 59 ms

As you can see the request asks ns1/ns2 what is the ip for www.photoblog.com and it returns well it's a cname to photoblog.com and here is the ip for that A record.