In a medium sized mixing bowl, combine the mayo, ketchup, relish, dried onion, vinegar, garlic, salt and pepper. Stir together until filly mixed and place in the refrigerator for at least an hour to allow the flavors to combine. Once the dressing is ready, mix with your desired amount of sauerkraut.
Preheat the oven to 375 degrees. Lightly mist a 9x13 casserole dish with cooking spray and set aside.
Unroll the can of crescent roll dough and press the seams together. Press the dough into the bottom of the prepared baking dish to cover the bottom. Sprinkle with 1 ½ teaspoons of the caraway seeds and press them into the dough a little bit. Bake for 8-10 minutes until dough is lightly golden.
When the dough is baked, remove from the oven and evenly layer the slices of corned beef over the surface of the dough. Spread the dressing and sauerkraut mixture over the top of the corned beef and lay the slices of swiss cheese to cover the top. Sprinkle the remaining ½ teaspoon of caraway seeds over the top of the cheese and place the casserole back in the oven for another 12-15 minutes until the cheese is melted, the casserole is heated through and the bottom is golden brown. Slice into 8 pieces and serve.