Tomato paste - why logically?
Tomatoes contain high levels of glutamic acid and its sodium salt (mono sodium glutimate or MSG). In fact, the pulp contains over 4 times as much as the flesh of the tomato.  In a tomato paste, the concentration of glutimates is even higher.  The "unique" flavor is not only concentrated tomato, but the umami that comes with it.  Tomato paste packs a very high umami punch that distinguishes it from fresh or canned tomatoes.

By the way, next time someone suggests that they want to avoid MSG, ask them if they also avoid tomatoes, Parmesan cheese, soy sauce, and many other ingredients where it is naturally occurring.  Lot's of good info here.