Add a teaspoon of whole peppercorns into a mortar and crush until fine. Add 2 teaspoons of sea salt and crush until incorporated into the peppercorns. Add 2 teaspoons of dried Greek oregano, 1 teaspoon of rosemary and 1 teaspoon of paprika and crush until completely combined. Set aside for now.
Cut the pork tenderloin into 1 inch pieces and lightly pound each piece with a meat tenderizer and transfer into a large bowl
Add 1/3 cup of a neutral oil, a tablespoon of dijon mustard, 4 cloves of finely minced garlic, 2 tablespoons of red wine vinegar, 2 tablespoons of lemon juice and 1 tablespoon of dijon mustard and massage until all of the pork is coated
Add the seasoning mixture and mix until evenly distributed
Let the pork marinade at room temperature for 60 minutes or chill for up to 12 hours
Thread the marinaded pieces of pork onto soaked bamboo skewers or metal skewers
Grill over medium to medium high heat for 3-4 minutes per side until caramelized on the outside and cooked through with an internal temperature of 145 degrees
Serve with sliced tomatoes, red onions, lemon wedges and tzatziki sauce