zest
/zɛst/
The outer skin of a citrus fruit, used as a flavouring or garnish.
The orange zest gives the strong flavor in this dish.
General vibrance of flavour.
I add zest to the meat by rubbing it with a spice mixture before grilling.
(by extension) Enthusiasm; keen enjoyment; relish; gusto.
The woody, thick skin enclosing the kernel of a walnut.