Trim away any excess fat from the flank steak and place on a baking sheet. Season generously with salt on both sides and then cover with the rub and pat in until it all adheres. Cover and cure in the refrigerator for at least 4 to 6 hours or for as long as overnight.
Remove the steak from the refrigerator an hour before grilling.
Preheat grill for direct cooking over high heat and as always, brush and oil grates before cooking.
Place steak on hot grill at a 45 degree angle to the grates. Cook for about 4 minutes per side for medium rare. Allow the steak to rest for about 10 minutes before slicing.
Meanwhile, brush bread with melted butter and grill toast on both sides until marked and golden.
Thinly slice across the grain of the meat with your knife tilted at an angle to give you nice wide slices.
Slather toasted bread with Swiss-Russian Spread and pile on the sliced steak and sauerkraut.
Recipe by Grilling Outdoor Recipes powered by Bull Outdoor Products at http://www.grillingoutdoorrecipes.com/your-game-day-sandwich-flank-steak-rubbed-with-pastrami-spices/