Preheat your oven to 375 degrees Fahrenheit. Lightly grease a 9×13 inch baking dish.
In a large bowl, combine the chopped corned beef, drained sauerkraut, Thousand Island dressing, and half of the shredded Swiss cheese. Mix these ingredients until they are evenly coated.
Arrange half of the cubed rye bread evenly over the bottom of the prepared baking dish.
Spread the corned beef and sauerkraut mixture over the layer of bread.
Top the mixture with the remaining half of the shredded Swiss cheese.
Place the remaining cubed rye bread on top of the cheese layer.
Drizzle the melted butter evenly over the top layer of bread cubes. Sprinkle with caraway seeds, if using.
Bake for 25 to 30 minutes, or until the casserole is hot throughout and the cheese is melted and bubbly.
Let the casserole rest for 5 minutes before you serve it warm.
Notes
Drain the sauerkraut thoroughly; excess liquid can make the bake watery. Press it dry between paper towels if needed.
You can substitute deli-style rye bread for the cubed bread.
For extra richness, mix 2 tablespoons of melted butter with the top layer of bread cubes instead of just drizzling.