Start by zesting the lemon and squeezing the juice fresh—this makes a noticeable difference in brightness. Mince the garlic finely and set aside with the parsley. In a small bowl, whisk together the lemon zest, lemon juice, minced garlic, red pepper flakes, 1/3 cup olive oil, and a pinch of salt and pepper. Let this mixture sit while you prep the other components so the flavors can meld together. This lemon oil is the soul of the dish, so don't skip making it fresh.
Trim the woody ends off the asparagus (snap them where they naturally break) and cut the remaining spears into 1-inch pieces. I like to keep the pieces fairly uniform so they cook evenly. Set the cut asparagus aside—you'll add it to the orzo near the end of cooking so it stays tender-crisp rather than mushy.
Bring the chicken broth and water to a rolling boil in a large pot. Add 1 tsp salt and the turmeric, which gives the orzo a beautiful golden color and subtle earthy note. Add the orzo and stir occasionally to prevent sticking. Cook for about 8-9 minutes, then add the prepared asparagus pieces to the pot. Continue cooking for another 2-3 minutes until the orzo is tender and has absorbed most of the liquid—it should be creamy, not dry or soupy. The turmeric will give you a warm, sophisticated backdrop for the bright lemon flavor.
Transfer the cooked orzo and asparagus to a large bowl, reserving about 1/4 cup of any remaining cooking liquid. Pour the lemon oil mixture from Step 1 over the warm orzo and toss gently but thoroughly, making sure everything is evenly coated. If the pasta seems too dry, add a splash of the reserved cooking liquid to loosen it. Taste and adjust seasoning with salt and pepper as needed. Scatter the crumbled feta cheese and remaining parsley over the top and give one more gentle toss.