Remove the silver skin. Start by using a sharp knife to lift it up and then grab it with a paper towel and pull to remove. It may take a few tries.
Once the silver skin is removed, cut each tenderloin into two halves or three sections (depending on the length of the tenderloins) of roughly the same size.
Remove the rosemary from it’s stems and finely chop. Mince the two cloves of garlic. Combine the rosemary, garlic, vinegar, brown sugar, salt, and pepper and then whisk in the olive oil.
Place all the tenderloin sections into a zip top bag and pour in the marinade. Let it marinate in the refrigerator for at least six hours, turning the bag about halfway through to make sure the sides are evenly coated.
You will want to set it on the counter about an hour before cooking in order to bring it to room temperature.
Lightly coat a frying pan with olive oil and heat it for about five minutes over medium-high heat. Add the tenderloin sections and cook a minute per side or until a nice brown crust develops.
Move the pork to a baking sheet lined with parchment. Place in the oven and cook for 12-15 minutes, until a thermometer inserted in the center reaches 135℉. Keep in mind that the smaller pieces may cook faster.
As the tenderloins finish cooking, remove them to a plate and tent with aluminum foil. Allow the meat to rest for at least 10 minutes before slicing and serving.