Place walnuts, cilantro*, Parmesan cheese, oil and salt in the bowl of a food processor and puree until smooth (about 1-2 minutes) to make the pesto.
Butterfly pork and pound until 1/4-inch thick. Spread cilantro pesto onto pork loin and roll up. Tie with butcher twine to hold it closed.
Sear pork in a hot skillet on all sides then place in a baking dish and bake for 30 minutes or until pork reaches an internal temperature of 145°F. Let rest 10 minutes.
Meanwhile, place 1 slice of mozzarella, topped with 1/4 cup mixed tomatoes, 1 tbsp. cilantro, 2 tsp. nuts, 2 tsp. oil, and 1 tsp. vinegar on each of 6 plates.
After allowing pork to rest for 10 minutes, cut into slices. Place sliced pork onto each plate.
*Basil may be substituted for cilantro, if desired. Tip: To butterfly pork tenderloin, place the tenderloin on a cutting board. Place your knife parallel to the board and carefully cut the meat lengthwise making sure not to cut all the way through. Remove the knife and open the meat