Seems like every culture has it own spin on fermented cabbage. Sauerkraut, kimchee and, obviously, curtido? On a recent trip to Central America we were fascinated by cabbage relish served with regional pupusas. Every restaurant and food stall had a slightly different take on the recipe and all were deservedly proud of their results.
The secret is to brine the cabbage in a solution of one tablespoon salt for every cup of water and half a cup of vinegar. Cover thinly sliced (pelo de bruja) cabbage with the mixture and leave on the counter to ferment a few days. You can eat it any time, but it will mellow and meld into something more complex over time. Do consider putting it in the fridge after a few days though.
You can experiment by adding anything you would ordinarily pickle to change the flavor. Thinly sliced onions, carrots and oregano are traditional, garlic is always nice, peppers for heat … Oh right and the type of cabbage is not particularly important, but I always use red for its eye catching color.