This recipe is modified from a combination of three recipes.
Begin with thick sliced fillets, about 1 and 3/ to 2 inches thick. The fillets should be room temperature.
Salt and pepper generously on all sides of the meat. I use fine ground sea salt and fresh ground black pepper.
Bring the oven to 250 degrees. Place the fillets in a dry cast iron skillet and place in the oven for 50 minutes. The end result will cook to medium turning 1 time half way through.
While waiting on the fillets, finely chop a large shallot. 
We will serve the fillets with mashed potatoes.
Here the fillets have been turned and pulled out of the oven. Rest the fillets on the sides of a bowl preventing them from resting in their juices and further cooking. We will use the juice from the bottom of the bowl. Resting will be about 3 minutes.
Place the skillet on the stovetop, set to medium and melt 2 tbls salted butter.
Bring the heat to high, turning the butter to a bubbling caramel color. Sear the fillets for 1 minute per side.
Remove the fillets, pour the juice from the resting bowl into the skillet and add 3/4 cup of red wine. Heat should be high. The wine will deglaze the pan and mix with the fat and juices from the steak. 
Add the shallots.
Continue to stir with a whisk reducing the mixture to a roux. 
Plate the mashed potatoes and fillet. Then, pour on the red wine shallot sauce.
Cooking the fillets in the oven prior to searing will allow for a completely consistent doneness with an exact temperature through the meat.
You may choose to add a slice of Bulgarian Feta or Maytag blue cheese.
