Step 1: Bring a large pot of salted water to a boil. Add the pasta and cook according to package directions until al dente.
Step 2: While the pasta cooks, heat the olive oil in a large skillet over medium heat. Add the minced garlic and red pepper flakes, sautéing for about 1 minute until fragrant.
Step 3: Add the asparagus pieces to the skillet. Season with a pinch of salt and pepper. Sauté for 3-5 minutes until the asparagus is tender-crisp.
Step 4: Before draining the pasta, carefully reserve 1/2 cup of the starchy pasta cooking water.
Step 5: Drain the pasta and add it directly into the skillet with the asparagus. Pour in the lemon juice, lemon zest, and half of the reserved pasta water.
Step 6: Toss everything together over low heat, gradually adding the Parmesan cheese and the remaining pasta water as needed to create a light sauce.
Step 7: Stir in the fresh parsley, adjust seasoning with salt and pepper, and serve immediately with extra cheese if desired.