Merquén (or merkén) is a spice powder that has become popular in Chilean cooking in the last several years. It is a traditional ingredient in Mapuche cooking, but has only recently debuted on the broader Chilean food scene. It is made from the dried, smoked cacho de cabra pepper, which is quite hot. Cacho de cabra means goat’s horn, and the pepper is, indeed, long and curved, like a goat’s horn. Note that the word cacho is slang for another part of the anatomy in the Caribbean, which leads to some interesting mistranslations of the pepper’s name.

Merquén is usually a blend of the smoked pepper, oregano, cumin, and salt, but the rich smoky flavor and spicy hot (picante) pepper dominate. It is available at some Whole Foods stores and also online. If you can’t find it, you might try substituting chipotle powder, which is also smoked but has a different flavor profile.

For the tartar sauce, I start with a blender mayonnaise, season with merquén, and then add capers, pickle, and green onion.

I fried the fish in caper oil and garnished with fried capers. This is a trick I learned from John Ash—frying takes the bite out of the capers and leaves a nicely…