1. Preheat your oven to 350°F (175°C) and grease a 9×13-inch baking dish.
2. In a large bowl, toss the cubed rye bread with the melted butter until the pieces are evenly coated. Spread half of the bread cubes in an even layer at the bottom of your prepared dish. This creates a buttery, crispy base layer that’s just divine.
3. Layer half of the chopped corned beef evenly over the bread.
4. Sprinkle 1 cup of the shredded Swiss cheese over the meat.
5. Distribute 1 cup of the drained sauerkraut evenly across the cheese layer.
6. Repeat the layers once more: remaining bread cubes, corned beef, Swiss cheese, and sauerkraut.
7. In a small bowl, whisk together mayonnaise, ketchup, horseradish, Worcestershire sauce, garlic powder, and black pepper until smooth. This sauce is where all the magic happens—it’s tangy, creamy, and packs that classic Reuben punch.
8. Pour the sauce evenly over the assembled layers in the baking dish, gently pressing down to help it soak through a bit.
9. If you like a little extra crunch and visual appeal, sprinkle poppy seeds on top.
10. Bake uncovered for 35-40 minutes, until the top is golden brown and bubbly. You’ll know it’s ready when the cheese is melted and the edges are crisp.
11. Let the bake rest for 5 minutes before serving—this helps it set and makes serving easier.

One tip I learned from my own kitchen experiments is to make sure the sauerkraut is well-drained. The last thing you want is a soggy bake! Also, don’t rush the resting time after baking; it lets the flavors meld beautifully and keeps everything from falling apart when you dish it out.