In a large bowl, combine the minced garlic, paprika, oregano, thyme, cayenne pepper (if using), salt, and black pepper.
Rub this mixture all over the pork slices, ensuring they are well-coated. Let marinate for at least 30 minutes or up to overnight in the refrigerator.
Heat the olive oil in a large skillet or Dutch oven over medium heat.
Add the chopped onion and cook until translucent, about 5 minutes.
Add the marinated pork slices to the skillet and cook until browned on both sides, about 4-5 minutes per side.
Pour in the white wine or white vinegar and chicken broth. Bring to a simmer.
Reduce the heat to low, cover, and cook for 20-30 minutes, or until the pork is tender and the flavors are well combined.
Remove the pork slices from the skillet and slice or shred them as desired.
Spoon some of the cooking liquid and onions onto Portuguese rolls or crusty bread, then top with the pork slices.
Optionally, garnish with pickled vegetables for extra flavor.
Enjoy your meal!