Brochas: Daf Lamed Vov amud beis

Rava said one who chews peppercorns on Yom Kippur is exempt (from the penalties associated with eating on Yom Kippur, because they are deemed not to be a food.)

...Then what does the Torah teach by stating "Food Tree?". It comes to include (in the law of Orlah i.e. forbidden consumption), (?the fruit of?) a tree whose wood and fruit are equal in taste. And this is the pepper tree.

... It is not difficult, this brysa (which holds peppercorns to be food is dealing with) moist ones; (while the ruling of Rava which considers them to be inedible is talking about) dry ones. 

The Rashba asks why we don't cite the case of the esrog, the wood of which also tastes like the fruit. He answers that we don't need a posuk to tell us that an esrog is fruit, while peppercorns because they are typically dry might well not be considered fruit.

The Ben haYehoyada points out that originally Hashem's intention was that all trees should have fruit and tree with the same taste. But the Earth chose to ignore this stricture because it knew that man would sin; nonetheless since G-d's intention will eventually be fulfilled, it was important that there should exist an example of a tree which had fulfilled the intent of the Creator.

He also explains that G-d's intent with the first Luchos (two tablets of commandments given by G-d to Moses) was that their internal spiritual essence should be akin to their external material appearance. When we sinned we caused the Torah available to us to be on a lower, more materialistic level. But in the future, matters will revert to their proper mode; at this point, the tree (which represents Torah - "Aitz Chaim He") and its fruit will once again taste the same. In the meantime, the pepper tree gives an example of what should have been.  Why is the pepper tree particularly  appropriate to fulfil this function? Because of the last part of the Brysa. If it is moist i.e. living and being renewed, it is food for the soul; if it is dry i.e. lifeless, it provides scant nourishment.