Preheat oven to 400 degrees F.
Take the beef tenderloin and drizzle with olive oil.¬† Season well all over with plenty of kosher salt and freshly ground¬† black pepper all over.¬† Make sure it is at room temperature before cooking.¬† Place a large cast-iron skillet over medium-high heat on the stove top and sear tenderloin all over.¬†¬† Place the whole pan in the oven and roast the tenderloin for 15-17 minutes (depending on how thick your tenderloin is).¬† An internal thermometer when inserted into the thickest part of the meat should read 130 degrees F for medium-rare.¬† If you want it medium, cook for a further 3 minutes in the oven.¬† Remove from the oven and tent with foil while you let it rest for 10 minutes before cutting.
BLENDER BEARNAISE SAUCE
Make the b√©arnaise reduction first. In a small saucepan, combine half of the tarragon, shallots, vinegar and wine over medium-high heat.¬† Bring to a simmer and cook until reduced by half. Remove from heat and set aside to cool.
Blend yolks and b√©arnaise reduction together.¬† With the blender running, add one third of the butter in a slow steady stream. Once it emulsifies, turn the blender speed up to high and add the remaining butter.¬† Add the remaining half bunch of fresh tarragon, season with salt and pepper and give it one more buzz.¬† Set aside in a warm spot to hold the sauce.
Edited: October 14th, 2009