We use ham, pickled cabbage and Swiss cheese for this non-traditional Reuben.
Preheat broiler, with rack set 4 inches from heat source. Lay bread on a broilerproof baking sheet; broil just until toasted, 1 to 2 minutes. Remove baking sheet from oven (leave broiler on).
Turn bread over; layer with ham, cabbage, and then Swiss cheese. Broil until cheese is golden, 4 to 6 minutes.
Meanwhile, in a small bowl, combine mayonnaise and ketchup; season with salt and pepper. Serve with Reuben sandwiches.