Insanely good beef tacos, and while not deliberately modeled after “barbacoa,” they came out most similar to barbacoa in the end. I took leftover oxtail meat, heated it with onion, poured in most of a can of Herdez salsa ranchera (a perennial standby for a fast meal), reduced it back to semi-dry, and served tacos with red cabbage, cilantro, raw onions, etc. on corn tortillas.
For those who are curious, the oxtail meat is insanely tasty, and has all the fat of pork shoulder, but a fantastic beef flavor. Heart-cloggingly good. Also a good way to use up leftovers after making beef stock (as was the H-o-Y pho).