Step 1

Make the pesto: Place the basil, arugula, nuts, cheese, garlic, and salt in the bowl of a food processor fitted with the blade attachment or blender. Process until finely chopped, about 1 minute. Scrape down the sides of the bowl. With the machine running, stream in the oil, blending until the pesto looks uniform; set aside.

Step 2

Make the salad: Place the onion in a large bowl, add 2 tablespoons of the pesto, and stir to combine; set aside.

Step 3

Pat the chicken dry with a paper towel. Generously season both sides with salt and pepper. Heat the oil in a large skillet over medium-high heat until shimmering. Add the chicken and cook undisturbed until browned on the bottom, 6 to 9 minutes. Flip and cook until browned on the second side and the internal temperature registers 165°F, 6 to 9 minutes. Transfer to a clean cutting board and tent with aluminum foil.

Step 4

Meanwhile, bring a pot of salted water to a boil. Add the green beans and cook until crisp-tender, about 2 minutes. Drain and set aside.

Step 5

Use a vegetable peeler, Y-peeler, or mandoline to slice the zucchini from top to bottom into ribbons about 1/16th of an inch thick. Add to the bowl with the onions. Add about 1/3 of the remaining pesto and toss to coat.

Step 6

Cut the chicken into 1-inch cubes. Add remaining pesto, chicken, green beans, and tomatoes to the bowl or vegetables and gently toss until everything is evenly coated. Serve at room temperature or chilled.