Note: Silverskin is a silvery-white connective tissue. It does not dissolve when the tenderloin is cooked, so it needs to be trimmed away. If the silverskin is not trimmed off, it will cause the tenderloins to curl up into the shape of a quarter moon. Score the meat at various points across the width of the tenderloin and set aside.
In a small bowl, combine the minced garlic and minced rosemary.
Rub the pork roasts with olive oil. Generously salt and pepper the meat and then rub the garlic/rosemary mixture over the meat.
Place the roasts in a single layer in an oven-proof baking dish with high sides. Add the Zinfandel wine to the pan until the pork roasts are about 3/4 covered (I used the whole bottle of wine), cover with plastic wrap and let marinate in the refrigerator approximately 2 to 4 hours, turning the roasts occasionally to distribute marinade. The pork roasts can also be marinated in a large re-sealable plastic bag and set into a shallow dish.
When ready to cook, remove from refrigerator. If marinating in a plastic bag, place roasts and marinade in an oven-proof baking dish with high sides.
Preheat oven to 350 degrees F. Bring roasts and wine marinade to room temperature before cooking, approximately 30 minutes.
Bake, uncovered, approximately 20 to 25 minutes or until a meat thermometer inserted into thickest part of the roast registers 140 degrees F.
Once the roasts are cooked to the proper temperature, remove from oven, remove the pork roast from the marinade, and transfer onto a cutting board; let roast stand 15 minutes before carving (meat temperature will rise 5 to 10 degrees after it is removed from the oven).
For the sauce: Pour the wine marinade into a large saucepan. Over medium-high heat, reduce the marinade mixture to approximately half (approximately 1 cup). Add any juices that accumulate from the pork roasts. Reduce heat to medium and whisk in the pieces of butter for flavor. Add salt and pepper to taste, if required; remove from heat. Do not strain the sauce.
Carve the pork tenderloin roasts and serve on a "puddle of sauce" on a serving platter. Place remaining sauce in a small serving bowl and serve on the side.
* Tenderloin comes in a sealed package with two small tenderloins, about 1 pound each.
** It is preferred that you use the same brand of wine that you will be drinking with the dinner.
Zinful Pork Tenderloin Recipe: https://whatscookingamerica.net/lindasandberg/entrees/zinfulporktenderloin.htm