Roast Beef with Port Sauce

1 whole beef tenderloin, tail end tucked under, tied every 3 inches

2 teaspoons coarse kosher salt

4 tablespoons (1/2 stick) chilled unsalted butter, divided

1/4 cup finely chopped shallots

3 tablespoons Cognac or brandy

1 fresh rosemary sprig

1 teaspoon coarsely cracked black pepper

1 cup ruby or tawny Port

Simple Homemade Beef Stock

2 tablespoons extra-virgin olive oil

2 tablespoons black peppercorns, coarsely cracked in mortar with pestle or in resealable plastic bag with mallet

Prepare the meat: (Optional but delivers best results)

It is best to start by sprinkling the beef  with coarse sea salt. Place in refrigerator uncovered for at least 24 hours for best results.

For sauce:

Melt 2 tablespoons butter in large saucepan over medium-low heat. Add shallots; sauté until soft, 3 minutes. Add Cognac, rosemary, and 1 teaspoon cracked pepper and cook until liquid evaporates,  Add Port; bring to simmer. Add all of beef stock. Boil until reduced to 1 1/2 cups, about 20 minutes. Strain into medium saucepan, pressing on solids to extract as much liquid as possible. Discard solids in strainer. DO AHEAD: Can be made 24 to 36 hours ahead. Cool slightly, then cover and chill.

For roasting:

Let beef stand at room temperature 1 hour before roasting. Position rack in center of oven and preheat to 425°F. Rub beef all over with oil; sprinkle with 2 tablespoons cracked peppercorns, pressing to adhere. Return beef to rack on baking sheet and roast until instant-read thermometer inserted into thickest part of meat registers 125°F for medium-rare (135°F to 140°F in thinnest part), about 30 minutes. Remove roast from oven and let rest 15 minutes.

Bring sauce to boil; whisk in remaining 2 tablespoons butter. Season sauce to taste with salt and pepper.