Recipe From PorkAndHealth.org
Butterfly pork tenderloin lengthwise. Flatten pork with the palm of your hand to achieve even thickness. cover with oil and season with cumin, salt and pepper.
Prepare grill for medium-high heat. Grill tomatillos, jalapenos and onion for about 5 to 10 minutes, turning often, until soft. Remove vegetables from grill. Seed and stem jalapenos. Add tomatoes, jalapenos and half the onions to a blender or food processor; blend until mixture becomes a thick paste. Transfer to a serving dish and mix in water and cilantro, adding, adding salt to taste.
Place pork on the grill and cook for 4-5 minutes on each side (about 20 minutes total time), until internal temperature as measured with an instant-read thermometer is 145 degrees Fahrenheit, followed by a 3-minute rest time. Slice pork and arrange on a warm serving tray. Spoon some of the tomatillo mixture over the pork and decorate with the remaining grilled onions. Garnish with cilantro. Serve pork with remaining sauce.
Tomatillos can be found in Mexican grocery stores and some larger markets or even at farmers markets. Serve with panfried potato slices and fresh seasonal fruit.