INSTRUCTIONS
1. Combine sugar, 2 teaspoons salt, and 1 teaspoon pepper in bowl. Cut each tenderloin in half horizontally, stopping ½ inch away from edge so halves remain attached. Open up tenderloins, cover with plastic wrap, and pound to 1/4-inch thickness. Trim any ragged edges to create rough rectangle about 10 inches by 6 inches. Sprinkle interior of each tenderloin with 1/8 teaspoon salt and 1/8 teaspoon pepper.
2. With long side of pork facing you, spread half of stuffing mixture over bottom half of one tenderloin followed by ½ cup spinach. Roll away from you into tight cylinder, taking care not to squeeze stuffing out ends. Position tenderloin seam side down, evenly space 5 pieces twine underneath, and tie. Repeat with remaining tenderloin, stuffing, and spinach.
3. Turn all burners to high, cover, and heat grill until hot, about 15 minutes. Leave primary burner on high and turn off other burner(s).
4. Clean and oil cooking grate. Coat pork with oil, then rub entire surface with brown sugar mixture. Place pork on cooler side of grill, cover, and cook until center of stuffing registers 140 degrees, 25 to 30 minutes, rotating pork once halfway through cooking.
5. Transfer pork to carving board, tent loosely with foil, and let rest for 5 to 10 minutes. Remove twine, slice pork into 1/2-inch-thick slices, and serve.
