Bring a large pot of well-salted water to a boil. Cook the orzo according to package directions, about 8 to 10 minutes, until just al dente. Drain and set aside. Do not rinse.

Heat 2 tablespoons of olive oil in a large skillet over medium-high heat until shimmering. Add the shrimp in a single layer and season with salt, pepper, and red pepper flakes if using. Cook for 2 to 3 minutes per side until pink and opaque. Do not overcrowd the pan. Remove from the skillet and set aside.

Reduce the heat to medium. Add the remaining 1 tablespoon of olive oil to the same skillet. Add the minced garlic and cook for about 30 seconds, stirring constantly, until fragrant. Watch carefully as garlic burns quickly and will turn the sauce bitter.

Pour in the broth, lemon juice, and lemon zest. Stir to combine and bring to a gentle simmer. Cook for 3 to 5 minutes until the flavors meld and the liquid reduces slightly.

Add the drained orzo and cooked shrimp back into the skillet. Stir gently until well combined and heated through, about 1 to 2 minutes.

Remove from heat and fold in the fresh parsley. Taste and adjust salt and pepper as needed. Serve immediately with freshly grated Parmesan on top if desired.