Weblink links to "url alias"

Hi,
I have FriendlyURLs enabled and am having trouble linking to the frontpage (base_url). I want to link to http://www.example.com, and not http://www.example.com/index.php (due to SEO reasons).

Whenever I input the address http://www.example.com in Tinymce as the Link URL it for some strange reason changes this to "undefined", and thus the link doesn’t work.
Then I thought I would create a weblink, that would contain the link to the site http://www.example.com, but instead of using what is specified as the Weblink it uses the URL alias, which cannot be http://www.example.com.

What to do?

Use the site_url as the WebLink target.

But it still grabs the "URL alias" as the link, instead of the "Weblink" for the weblink that I have set up... Is there any way to make it take the Weblink and not the URL alias?