Código Apache:
Ver originalOptions -indexes +FollowSymLinks
DirectoryIndex sitemap.php
# www.miweb.com ····> miweb.com/sistema.php
rewritecond %{http_host} ^www.miweb.com[nc]
rewriterule ^(.*)$ http://miweb.com/$1 [r=301,nc]
# redirigir todos al sitemap
RewriteCond %{REQUEST_FILENAME} !sitemap.php
RewriteRule ^(.*)$ /sitemap.php[r=302,L]
Saludos