Cook the Orzo: Bring a large pot of water to a boil and add 1 tablespoon of salt. Add the orzo and cook until al dente, according to package instructions. Drain the orzo and rinse with cold water, until the orzo itself comes to room temperature.

Make the Dressing: Whisk the pesto and vinegar together in the base of a large bowl until a smooth texture forms.

Mix: Add the orzo, tomatoes, and chickpeas to the bowl and mix until evenly combined. Add the basil, feta (optional), pine nuts, and arugula. Gently fold into the salad. Season with additional salt to taste, if necessary.

Serve: Serve immediately, or chill in the fridge for 15 minutes before serving. Leftovers can be stored in an airtight container in the refrigerator for up to 5 days.