1. Heat oven to 350 degrees F. Coat 13 x 9 x 2-inch baking dish with nonstick cooking spray.
2. Cook noodles following package directions. Drain and toss with 2 tablespoons of the butter. Place in prepared dish; top with sauerkraut, then corned beef. In a bowl, mix mayonnaise, ketchup, pickle and onion. Spread over corned beef. Top with tomato and cheese.
3. Pour milk evenly over the top. Melt remaining 2 tablespoons butter and toss with rye cracker crumbs and caraway seeds; sprinkle over the top. Bake at 350 degrees F for 45 minutes. Let stand 10 minutes, then serve.