Hi !
It’s not really possible to leave Lima (which is what I’m about to do) without a reference to the most exquisite of all dishes: the ceviche (classico, with sea bass been my favorite).
First, about the recipe: marinate the freshest pieces (cubes of 1cm3) of sea bass fillet (or Atlantic cod, tuna, salmon, …) in lime and coriander, add some choclo and some cold (but cooked) sweet potatoes. You can of course spice it a little bit, but definitely using Peruvian peppers, which burn reasonably the mouth and not the stomach.
If the fish is insanely fresh, marinate only for a few minutes. The center should remain raw, while a nice white thin layer of cooked fish should form in contact of the lime. If the fish is less fresh, then marinate it longer.
When traveling the Peru, you should really only trust it on the coast, in restaurant. On the beach it is risky, the quality of the fish is not good. La Mar in Lima (or Astrid y Gaston) is your safest bet, they just get the freshest fish.
There’s a vegetal version which is more popular on the mountain, but nothing beats the fish one.
Enjoy (or not) and stay tuned !