Location: Casa Guedes Tradicional, Praça dos Poveiros 130, 4000-393 Porto, Portugal
Getting there: Trindade station
No-frills local institution, cash only, queue outside
Specialty: Sándwich de pernil — roast pork with goat cheese and port onions
Price range: $ (~8)
Pro tip: Go to the original Poveiros Square location, not the touristy copy
Recommended by @Pitufueros