In a small bowl, mix together paprika, achiote, cumin, garlic, salt, and pepper. Rub on all sides of pork slices. Add onions and toss. Cover and marinade in refrigerator overnight.
When ready to cook, place pork in Instant Pot. Add beer. Cook on high pressure for 30 minutes. Natural release for 15 minutes, then release pressure. Select "Cancel." Remove pork from Instant Pot. Select "Saute" and reduce sauce for 7-8 minutes. Season to taste with salt and pepper.
Shred pork using two forks. Pour reduced sauce on top and serve with tacos, arepas, burrito bowls or nachos.
Adapted from My Colombian Recipes