Toast the walnuts in a dry skillet over medium heat for about 3–4 minutes, stirring frequently until they're fragrant and lightly golden. Chop coarsely and set aside.

Zest and juice the lemons into a bowl. Tear the fresh basil, halve the cherry tomatoes, and grate the parmesan cheese.

In a large pot, bring salted water to a boil and add the pasta. Cook according to package instructions until al dente, about 8–10 minutes, then drain.

In a mixing bowl, combine lemon juice, white balsamic vinegar, Dijon mustard, and a pinch of salt and pepper. Whisk while drizzling in the olive oil until emulsified.

Add cooled pasta to the dressing and toss gently to coat.

Fold in parmesan, walnuts, cherry tomatoes, and basil. Mix gently.

Add arugula last, folding it in carefully to maintain its crispness. Taste and adjust seasoning as needed.

Serve immediately or let sit for 15-30 minutes for flavors to meld. Store in the fridge for up to 3 days, adding arugula just before serving.