Freeze and thaw the pork neck to make it easier to cut into thin strips. Trim excess fat.
Peel the onions, cut them in half lengthways, and slice into very fine rings.
In a bowl, combine the cornstarch, oregano, parsley, 2 cloves garlic, cayenne pepper, cinnamon, salt, freshly ground pepper, paprika powder, sugar, rosemary, thyme, and nutmeg.
In another bowl, mix the 200 ml olive oil with the lemon juice and zest.
In a large bowl, combine the pork strips and onions. Massage the dry spice mixture thoroughly into the meat.
Pour the lemon oil mixture over the meat and onions, then mix well.
Cover the bowl and refrigerate the marinated pork and onions for 24 hours.
Peel the cucumber, grate it finely, and squeeze out excess moisture using a clean cloth.
In a bowl, mix the grated cucumber with the 4 cloves garlic, 400 g Greek yogurt, and a splash of olive oil. Season with salt and freshly ground pepper to taste.
Cover the tzatziki and refrigerate for 24 hours.
Remove the pork from the marinade and drain off excess oil.
Heat a large frying pan over medium-high heat. Fry the pork strips without adding additional fat. As the pork cooks and releases fat, remove excess fat from the pan with a skimmer. Continue frying until the pork reaches an internal temperature of 63°C (145°F).
Serve with tzatziki and french fries or tomato rice.