How do I cook a 6 pound beef tenderloin

Over the years, I have found ATK's way of oven roasting at 300 degrees until 135 internal temp and then searing in a 12" skillet on the stovetop...the best ever! ATK also has a great stuffed tenderloin recipe; but my family loves the low and slow w/a sear at the end...the best with Bearnaise:-)

Even a 5 lb tenderloin should need no additional prep other then to take the narrow end and double it back a few inches to create an even size for even roasting.

My favorite way to roast if you have an oven thermometer.
Bring beef to room temp. Rub with olive oil, garlic, and pepper.
Preheat oven to 500 degrees. Place roast in pan and into well heated oven for 15 min. Warning do not open door of oven!!! Cut temp back to 200. Continue roasting until you have an internal temp of 125 -130. Remove from oven and allow to rest about 20 - 30 min. This is for a rare roast adjust accordingly. If you have folks who like well done - tell them to dine elsewhere... jus kidding... for those few well done lover do not tie back the tail. It will be well whilst the butt is rare to medium rare.

Oh, I had that issue once, haha. I had to cut mine up into about 8 pieces - some for crock pot, some for pork chops, etc. When I do crock pot, I add potatoes, herbs, pearl onions, sometimes tomatoes.

That is a great recipe. Here's another really good one: http://food52.com/recipes/14700-mom-s-garlic-rubbed-roast-filet-of-beef-with-mushroom-sauce

Here's a very nice recipe for beef tenderloin. It calls for a 3 pound tenderloin. To make this I would cut your piece in half; double the other ingredients and roast per directions here
http://food52.com/recipes/14725-porcini-and-rosemary-crusted-beef-tenderloin-with-port-wine-sauce