Place the pork tenderloins in a resealable plastic bag or a shallow dish and pour the pineapple juice over them. Seal or cover and refrigerate for at least 2 hours, or overnight for maximum flavor.

When you're ready to cook, remove the pork from the marinade and pat it dry thoroughly with paper towels. Discard the used marinade. Season the tenderloins generously on all sides with salt and black pepper, then rub them with the teaspoon of oil.

Preheat a grill pan or outdoor grill over high heat until very hot. Place the tenderloins on the grill and let them sear undisturbed for 4–5 minutes on one side. Once they develop a nice crust, turn them to brown all sides evenly. If your tenderloins are thicker or heavier than average, you can reduce the heat to medium, add ¼ cup of water (60 ml), and cover the grill or pan to ensure the inside cooks through without burning the outside. The total cooking time should be about 20–25 minutes, depending on the thickness. Use a meat thermometer to check that the internal temperature reaches 145°F (63°C).

While the pork is cooking, make the pineapple salsa. In a bowl, combine the diced pineapple, red onion, red bell pepper, lime juice, and olive oil. Stir gently until well mixed. Taste and add a pinch of salt if needed. Garnish with fresh cilantro just before serving.

Once the pork is done cooking, remove it from the grill and let it rest on a cutting board for at least 5 minutes. After resting, slice each tenderloin lengthwise (like a hot dog bun) and spoon the pineapple salsa into the center, or slice into medallions and top each piece with salsa.

Serve immediately, paired with a fresh salad or side of your choice.