I don't even know what ceviche is.

If you have decent bread for toasting, and you are in a hurry and can't be arsed to make anything that takes more than seven minutes, make this:

Drain two cans of mackerel in oil. Chuck the oil away.
Put mackerel in blender. I care not a jot, any blender will do.
Add a dash of Tabasco, a teaspoon of hot mustard, a tablespoon of creme fraiche, a grinding of pepper (salt not needed) and the juice of three-quarters of an average lemon. Blitz in your blender. Stir it around and put it in an ungodly little pot
. Ideally, I'd say leave it until tomorrow. But an hour or three is transformative.