Wash the arugula thoroughly under cold water and spin it dry in a salad spinner or pat it down with a clean towel. Slice the apple thinly, discarding the core.

If your walnuts aren’t already toasted, heat a dry skillet over medium heat. Add the walnuts and stir frequently for about 5-7 minutes or until they are golden brown and emit a nutty aroma. Remove from heat and let cool.

In a small bowl, whisk together olive oil, balsamic vinegar, salt, and pepper until emulsified.

In a large mixing bowl, combine the arugula, sliced apples, and toasted walnuts. Drizzle the dressing over the salad and toss gently to coat everything evenly.

Finally, sprinkle the crumbled feta cheese on top of the salad. Give it one last gentle toss to mix it all together.

Transfer the salad to a serving bowl or individual plates, and dig in!