Preheat oven to 350ยบ. Drain sauerkraut and mix with salad dressing, onion, garlic salt, and tomatoes. Place in buttered 9-x-13-inch casserole dish. Top with diced corned beef and then cheese. Unroll crescent rolls and press together, joining seams. Place on top of casserole to form crust. Bake for 30 minutes.