Trim the pork of any excess flat and sinew. Cut into approximately 1.5in/3cm dice - if using pork tenderloin, cut in half lengthwise then cut into slices.
Mix together all the remaining ingredients - the spices (cumin, coriander, oregano, paprika, turmeric, fennel seeds, allspice and cinnamon), salt, olive oil, lemon juice, garlic and pepper into a paste. Add the diced pork, ensure it is well covered with the marinade then cover and refrigerate for at least 2 hours, but overnight would also be good.
When ready to cook, thread the pork onto skewers - try to put the pieces on so that they flatten out slightly and are even in thickness so they cook evenly.
Cook on the grill for a few minutes each side until just charring and cooked through - exact cooking time will vary depending on thickness of pork and grill heat etc.
Serve with other tapas of your choice (eg tortilla, pan tomate, salad) and enjoy!
Video
Notes
Note prep time does not include marinading time. If using wooden skewers, make sure you soak them for at least 30 minutes before using.