Grind the pork in a meat grinder and place in a medium bowl. Season with salt and black pepper. Let rest at room temperature for 15 minutes.
Using plastic wrap, shape the seasoned pork into a log about 3 inches in diameter. Wrap tightly to maintain its shape and refrigerate overnight.
The next day, preheat a water bath to approximately 150°F. Place the wrapped pork log in the water bath and cook for about 3 hours. Refrigerate until completely cool.
Preheat oven to 350°F. Remove the pork from the plastic wrap, transfer to a wire rack and roast for 30 minutes.
While the pork is roasting, combine the yellow onion, garlic, aji panca peppers, red wine vinegar, cumin, turmeric, salt and black pepper in a blender. Blend until smooth, adding olive oil as needed to form a paste.
After the pork has roasted for 30 minutes, remove it from the oven and carefully poke holes throughout. Coat the pork evenly with the aji panca pepper paste.
Return to the oven and roast for an additional 20 minutes, or until the desired color is achieved and the pork is fully cooked. Let cool slightly before slicing.
To Serve
Slice the pork and serve with salsa criolla, huancaína sauce and toasted ciabatta bread.
