Rinse the farro under cold water. Place it in a saucepan with 2 cups water and bring to a boil. Reduce heat, cover, and simmer for 20 minutes until tender. Drain any excess water and set aside.

Heat a grill to medium-high. Rub the pork tenderloin with 1 tablespoon olive oil, then season with salt and black pepper. Grill the pork for 15 to 18 minutes, turning every few minutes, until it reaches an internal temperature of 145°F. Let it rest for 5 minutes before slicing.

In a large bowl, combine the sliced apples and fennel. Add the remaining 2 tablespoons olive oil and lemon juice. Toss gently to coat.

Divide the cooked farro among four plates. Top each with slices of grilled pork and a generous portion of the apple-fennel salad. Sprinkle with chopped parsley before serving.