In a small bowl, stir together the Greek spice mix and set aside.
In a large bowl, add the ground pork. Drizzle with juice of 1/2 lemon and scatter the minced garlic over-top. Sprinkle the Greek spice mix over-top. Using your hands, mix together, until the spice mix and seasoning is evenly distributed through the pork. Do not over-work.
Form pork mixture into 5 equal-sized patties and if time permits, place on a plate, cover with plastic wrap and refrigerate until needed (allows the spices to flavour the pork).
Season the outside of the patties with a sprinkling of salt and pepper. Cook pork patties on the BBQ (grease the grill), or in a little oil in a skillet or in a grill pan on the stove-top. Cook until thoroughly cooked through, until there is no pink inside and until the meat reaches an internal temperature of at least 160F. *Important to cook thoroughly.
Toast hamburger buns. Place some leaf lettuce on the bottom half of the bun. Top with a dollop of tzatziki sauce, then top with a cooked pork patty. Top pork patty with crumbled feta, sliced red onion and tomato slices.
Be sure to read the "Cook's Notes" included with this post, where I share some valuable tips, options, substitutions and variations for this recipe!