Step 1

Bring the roast to room temperature about 1 hour before cooking.

Step 2

Preheat the oven to 450 degrees F.

Step 3

Sprinkle the roast on all sides with kosher salt and pepper. Brush the roast with the mustard. Combine the oregano, parsley, sage and thyme in a bowl and sprinkle it on the roast, followed by a liberal amount of kosher salt and pepper. Place the rosemary on a the roasting rack and place the roast on top of the rosemary. Add the broth to the roasting pan. Roast the meat for 20 minutes, then reduce the heat to 300 degrees F and continue to roast until the internal temperature reaches 110 to 115 degrees F for rare, about 1 hour.

Step 4

Meanwhile, combine the sour cream, mayonnaise, horseradish and vinegar. Season with kosher salt and pepper. Refrigerate until ready to use.

Step 5

Allow the meat to rest, uncovered, for 1 hour. Pour the liquid from the bottom of the roasting pan into a small pot and let simmer for 20 minutes to reduce. Keep warm.

Step 6

When ready to slice, preheat the oven to 350 degrees F. Brush the tops of the rolls with the melted butter and sprinkle with the caraway seeds and some pretzel salt. Toast the rolls slightly for about 5 minutes.

Step 7

Spread the horseradish cream on the interiors of the rolls. Top with the onions, if using. Slice the meat paper-thin, about 4 ounces per sandwich. Dip the sliced meat into the warm jus, then add to the roll bottoms. Top with the roll tops. Serve with the remaining jus for dipping if desired.