Beet, Sauerkraut, and Swiss Reuben Sandwiches
Combine the mayonnaise, ketchup, and pickle relish in a small bowl.
Spread the mayonnaise mixture on 4 slices of the bread. Top with the Swiss cheese, beets, and sauerkraut. Top with the remaining bread, to form the sandwiches.
Melt ½ tablespoon of the butter in a large skillet over medium heat. Cook 2 of the sandwiches, covered and turning once, until the cheese is melted and the bread is golden brown, 3 to 4 minutes per side. Repeat with the remaining butter and sandwiches. (Reduce heat if the bread gets too dark before the cheese is melted.)