Wash the 2 bunches of arugula and dry them in a salad spinner.
Cut them into thin strips and put them in a bowl.
Cut the 1/2 pound of Gruyere cheese into cubes or strips.
Wash the two apples, cut them into quarters, then remove the seeds and cores. Cut the apples in cubes or strips too.
Put the cheese and apples in the bowl, and sprinkle the 1/2 cup of shelled walnuts over them.
Wisk the 1/4 cup of lemon juice, 1/2 cup of extra-virgin olive oil, and salt together, and pour over the salad. Toss and serve.