• 1 c. vinegar or kefir (see Note)
Cut meat into chunks 11/2 to 2 inches square. Rub each piece with salt and black pepper, along with whatever other seasonings are desired.
Cover the bottom of a large stew pot with a layer of meat, then add a layer of onion wedges and strew with coarsely chopped cilantro and flat-leaf parsley. Press down firmly and add another layer of meat, then onions and herbs. Repeat until all the meat is layered between onions and herbs.
Pour vinegar or kefir over the top and cover tightly. Refrigerate for 3 to 4 hours or overnight.
Prepare grill. Thread the cubes onto metal skewers, alternating with the onion wedges. Place over smoking embers on an open grill and roast, turning often, for 15 to 20 minutes, until the meat is no longer pink inside. If flames appear, quickly douse them with water or, preferably, wine.