Start by bringing a large pot of salted water to a rolling boil. Add the whole wheat pasta and cook for 8-10 minutes until al dente. Drain and rinse under cold water.

In a spacious bowl, combine cooled pasta with fresh arugula, halved cherry tomatoes, diced cucumber, sliced red onion, and crumbled feta cheese. Toss gently to blend.

In a small bowl, whisk together olive oil, lemon juice, Dijon mustard, salt, pepper, and optional red pepper flakes until smooth.

Pour the dressing over the salad mixture and toss gently using tongs.

Cover the bowl and refrigerate for at least 30 minutes to let flavors meld.

Before serving, toss salad lightly again and serve chilled or at room temperature, optionally garnished with feta or lemon slices.