In a small bowl, mix 4 tablespoons dressing with the sauerkraut.
Warm skillet over medium heat. Butter one side each of the rye bread slices and place (buttered-side down) in the skillet.
Place one slice of cheese on each slice of bread. Top two with corned beef and sauerkraut mixture.
Spoon remaining dressing on corned beef, then top with the remaining slices of bread and cheese.
Cook until heated and cheese is soft.
Official Omaha Blackstone Reuben Sandwich from Crescent Moon. Recipe adapted from Frank's Kraut website.