The Reuben sandwich is an American hot sandwich composed of corned beef, Swiss cheese, sauerkraut, and Russian dressing, grilled between slices of rye bread. Several variants exist.

What is the meat in a reuben sandwich? Let's have some stream of consciousness first.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
The relevant sentence in the passage is: The Reuben sandwich is an American hot sandwich composed of corned beef, Swiss cheese, sauerkraut, and Russian dressing, grilled between slices of rye bread. So, the answer is corned beef.