Prep the pork. Remove the pork tenderloins from their package and pat them very dry with paper towels. Trim away any silver skin and connective tissue.
Make the marinade. In a small food processor, combine the garlic, olive oil, red wine vinegar, cumin, salt and pepper and blend until smooth. You may need to scrape down the sides and then blend again to get a smooth marinade.
Marinate the pork. Pour the marinade into a gallon ziplock bag and add the pork tenderloin. Seal the bag, removing as much of the air as you can in the process, and massage the marinade into the pork. Transfer to the fridge for at least 2 hours, up to 24 hours.
Make the chimichurri. Combine all the ingredients in a small bowl and mix well. Season with salt and pepper. Plan to make the chimichurri at least one hour before serving so that the flavors can really meld.
Prep the grill. Before using your grill, make sure to clean the grates of any food and debris. Lightly grease the grates with nonstick spray. Preheat an outdoor grill to medium-high until the temperature reaches 400 F.
Grill. Remove the tenderloins from the marinade and shake off any excess. Lay the tenderloins on the hot grill and grill for 3-4 minutes per side, until lightly charred. Turn off 1-2 of the burners and move the tenderloins to the cooler side of the grill. Cover and grill until the internal temperature reaches 145 F. Remove from the grill and let the pork rest for 10 minutes before slicing.
Serve. Serve the sliced grilled pork topped with the chimichurri and flaky sea salt, if desired.