Place the farro, apple cider, bay leaves, 2 teaspoons salt, and 2 cups water in a medium saucepan, bring to a boil, lower the heat, and simmer uncovered for about 30 minutes, until the farro is tender. (If all the liquid is absorbed before the farro is tender, add a little more water.) Drain the farro and transfer to a large serving bowl. Discard the bay leaves.
Meanwhile, in a small measuring cup, whisk together the olive oil, lemon juice, 1 teaspoon salt, and 1/2 teaspoon pepper. Stir the vinaigrette into the warm farro and set aside for at least 15 minutes to cool.
Before serving, stir in the pistachios, parsley, mint, tomatoes, and radishes. Add the arugula and lightly fold in the Parmesan so as not to break it up too much. Sprinkle with the sea salt and serve immediately.