Depending on what else swiss and caramelized onions are paired with, the flavors that are highlighted are different. In this sandwich, there is almost a sweet, nutty and earthy flavor that is brought out. Pair that with the salty, smokey, and peppery taste of the pastrami, this sandwich becomes an instant favorite.
The pastrami I used here was from Trader Joes. I will say that although I really liked it, I haven't had tons of other pastrami to compare it to. Also, I used sourdough bread as I abhor rye bread which apparently is the more popular for this kind of thing.