Medium-rare is the best temperature for filet mignon and beef tenderloin. If that's a little too under-done for you, you can go as far as medium. You don't want to cook this beautiful and expensive cut of meat to more than medium. For medium-rare, cook it to 130°F-135°F. For medium, cook to 135°F-140°F. And for rare, cook it to 120°F-125°F.