Bring a large pot of salted water to a boil. Add the pasta and cook until al dente. Drain the pasta and reserve 1/2 cup of the cooking liquid.
Add 2 tablespoons olive oil to a large stockpot set over medium-low heat. Add the asparagus, peas and 1/2 teaspoon kosher salt and cook, stirring, until the asparagus are crisp-tender, about 3 minutes. Add the zucchini and cook, stirring, an additional 2 minutes. Transfer the vegetables to a bowl.
Return the stockpot to medium-low heat. Add the remaining 2 tablespoons olive oil, garlic and crushed red pepper flakes (optional). Cook, stirring, until golden brown, about 2 minutes. Add the lemon zest, lemon juice and the reserved pasta water. Simmer until reduced by half, 3 to 5 minutes. Remove the stockpot from the heat and stir in the Parmesan cheese.
Return the vegetables to the skillet along with the pasta and toss to combine. Taste and season with salt and pepper.
Garnish the pasta with chives, additional Parmesan cheese and a squeeze of fresh lemon juice.
★ Did you make this recipe? Don't forget to give it a star rating below!