Mix the ancho chili powder, salt, oregano, cumin, pepper, cinnamon and allspice in a medium bowl.
Add the pork, onion, vinegar and cilantro.
Using your hands, mix all the ingredients together.
Let the pork sit for 30 minutes to let the rub mixture infuse all the flavors into the pork.
Heat olive oil in a cast iron skillet.
Add the pork and cook over moderately high heat until browned on all sides. This should take about 10-15 minutes. Stir it around every few minutes, so the pork browns evenly on all sides. This is when your family will probably come running into the kitchen begging for a bite! Tell them dinner will be ready in 15 minutes......and then ask them to go set the table to distract them from trying to steal bites.
Transfer the pork to a serving bowl, sprinkle with cheese and some more fresh cilantro.
Serve with warmed tortillas and your favorite toppings.