2/3 cup balsamic vinegar
1/3 cup olive oil
2 tablespoons soy sauce
4 1/2 teaspoons firmly packed golden brown sugar
3/4 teaspoons freshly ground pepper
1/2 cup finely chopped fresh rosemary
5 garlic cloves chopped
2 pork tenderloins about 2 1/2 lb. total,
Salt to taste
To make the balsamic-rosemary marinade, in a food processor, combine the vinegar, olive oil, soy sauce, brown sugar and pepper and pulse until blended. With the motor running, drop the rosemary and garlic through the feed tube and continue to process until fairly smooth. Place the tenderloins in a nonreactive dish and pour the marinade over them. Cover and let stand at room temperature, turning occasionally, for up to 2 hours.
Prepare a charcoal or gas grill for direct grilling over medium-high heat. Remove the tenderloins from the marinade, reserving the marinade.
Grill the meat over the hottest part of a charcoal fire or directly over the heat elements of a gas grill. Turn the meat every 4 to 5 minutes and baste with the marinade for up to 5 minutes before the meat is done until cooked to your liking, about 20 minutes total for medium (slightly pink at the center and juicy).
To test for doneness, insert an instant-read thermometer into the thickest part of the tenderloins; it should register 140°F. The temperature will rise another 5° to 10°F while the meat is resting.
Transfer the tenderloins to a carving board, cover loosely with aluminum foil and let rest for 5 minutes. Carve into slices across the grain and at an angle to the cutting board. Season with salt. Serve the tenderloins hot, warm or at room temperature.