Cook the pasta: Bring a large pot of salted water to a boil.
Add pasta and cook until just al dente. Reserve 1/2 cup pasta water, then drain and rinse under cool water to stop cooking.
Prep the veggies: Halve cherry tomatoes. Blanch green beans in the pasta water for 2–3 minutes until crisp-tender; cool under cold water.
Slice onion and chop cucumber.
Make the dairy-free pesto: In a blender or food processor, add basil, nuts/seeds, garlic, lemon zest and juice, nutritional yeast, and a pinch of salt and pepper. Pulse to break down. With the motor running, stream in olive oil until creamy.
Add 1–3 tablespoons reserved pasta water to loosen if needed.
Adjust seasoning: Taste the pesto. Add more lemon for brightness, salt for balance, or nutritional yeast for savoriness. For extra umami, blend in miso or capers.
Toss the salad: In a large bowl, combine cooled pasta, tomatoes, green beans, arugula or spinach, cucumber, red onion, and chickpeas or edamame if using.
Spoon over the pesto and toss until everything is well coated. Add a splash of pasta water if it seems thick.
Finish and garnish: Season with salt, pepper, and a pinch of red pepper flakes. Add a squeeze of lemon.
Top with extra basil and toasted nuts or seeds.
Rest (optional): Let the salad sit 10–15 minutes so the flavors meld. Serve chilled or at room temperature.