Place beef on a pan, and rub with salt. Place meat on a rack or twisted foil so air can circulate under roast, and transfer to the fridge for 24 to 48 hours.

Remove from the refrigerator and let it rest for a few hours to come to room temperature (optional).

Preheat the oven to 300 degrees F (150 degrees C).

Transfer roast into a roasting pan, preferably on a rack.

Mix butter with coarse salt, pepper, and cayenne in a small bowl and spread onto the sides and top of the roast. Then add more salt to the top. Pour water into the bottom of the pan.

Roast in the preheated oven until internal temperature is 115 to 120 degrees F (46 to 48 degrees C), about 1 hour and 20 minutes (about 20 minutes per pound). Remove from the oven, cover with foil and let rest for at least 20 minutes before serving.

Drippings from the pan can be deglazed with broth or water, and served alongside meat.