A new window opens by default with the home page(s).
If you want a blank window then you need to open an about:blank page in a new window.
You can do that with a bookmark that you open with a Shift+ left-click in a new window.
Otherwise you need to set the Home page to a blank page and use a bookmark to open the preferred Home page in a new tab.

I only need my home pages when I launch firefox. When I need a new browser window, my "essential" home pages are already open. To open them in a new browser just makes for CONFUSION! We need the option of opening a blank page with Ctrl-N - without having to go select a bookmark of something that I'm not interested in looking at. PLEASE reconsider the programming for Ctrl-N.