The man page doesn't give any hints about what a SPEC file is
or where it might be found. I had to guess.  In doing that,
I discovered this feature:  rpm creates file named
'tar: *.spec: Not found in archive' instead of printing the
error to stderr.

[root@desk /root]# ls -al /usr/src/redhat/SPECS/
total 24
drwxr-xr-x   2 root     root         4096 Jan 16 01:13 .
drwxr-xr-x   7 root     root         4096 Jan  9 13:43 ..
-rw-rw-r--   1 root     root        13622 Dec 14 10:38 linuxconf.spec
[root@desk /root]# rpm -tc
/usr/src/redhat/SOURCES/linuxconf-1.16r10.src.tar.gz
Name field must be present in package: (main package)
Version field must be present in package: (main package)
Release field must be present in package: (main package)
Summary field must be present in package: (main package)
Group field must be present in package: (main package)
License field must be present in package: (main package)
[root@desk /root]# ls -al /usr/src/redhat/SPECS/
total 24
drwxr-xr-x   2 root     root         4096 Jan 16 01:14 .
drwxr-xr-x   7 root     root         4096 Jan  9 13:43 ..
-rw-rw-r--   1 root     root        13622 Dec 14 10:38 linuxconf.spec
-rw-r--r--   1 root     root            0 Jan 16 01:14 tar: *.spec: Not
found in archive
[root@desk /root]#