Well, after many trials and errors it’s now solved.
Below my .htaccess files, the first one in the root of my domain the second one in wordpress directory.
I also had to set “WordPress address” and “Blog address” under “Options – General” to http://rafael-lueder.com/blog
I had a lot of help from richardk at http://forum.modrewrite.com/
<IfModule mod_rewrite.c>
RewriteEngine on
RewriteCond %{HTTP_HOST} ^(www\.)?rafael-lueder\.com$ [NC]
RewriteCond %{DOCUMENT_ROOT}/rafael%{REQUEST_URI}/ -d
RewriteRule [^/]$ %{REQUEST_URI}/ [R=301,L]
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteCond %{HTTP_HOST} ^(www\.)?rafael-lueder\.com$ [NC]
RewriteRule ^(.*)$ /rafael/$1 [QSA,L]
</IfModule>
<IfModule mod_rewrite.c>
RewriteEngine on
RewriteBase /rafael/blog/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /rafael/blog/index.php [L]
</IfModule>
