1In a blender, combine the achiote paste, sour orange juice, white vinegar, garlic cloves, Mexican oregano, cumin seeds, black peppercorns, cloves, Mexican cinnamon stick, and salt. Blend until a smooth marinade forms.
2Place the pork shoulder cubes in a large non-reactive bowl. Pour the blended marinade over the pork shoulder, ensuring all pieces are well coated. Cover and refrigerate for at least 4 hours, or preferably overnight.