Pat the shrimp completely dry with paper towels and season them lightly with salt and pepper. Set aside on a plate. Dry shrimp sear properly instead of steaming, so do not skip this step.

Melt 2 tablespoons of the butter in a large deep skillet over medium heat. Add the dry orzo and stir it around for about 2 minutes until it smells nutty and turns a light golden color. Keep an eye on it because orzo can go from golden to burnt quickly.

Add the minced garlic and red pepper flakes if using. Stir constantly for 30 seconds until fragrant. Pour in the chicken broth and bring it to a gentle boil. Season with the salt and pepper. Reduce heat to medium-low, cover the skillet, and cook for 10 to 12 minutes, stirring once halfway through, until the orzo is just tender and most of the broth is absorbed. The mixture should look creamy, not soupy and not dry.

Push the orzo to the edges of the pan and add the remaining 1 tablespoon of butter to the center. Once it melts, add the shrimp in a single layer. Cook for 2 minutes on the first side without moving them, then flip each one with tongs. Cook 1 to 2 minutes more until they are pink and curled into a loose C shape. An overcooked shrimp curls into a tight O, so pull them off heat as soon as they look done.

Remove the pan from heat. Squeeze the lemon juice over everything, add the lemon zest, and scatter the parsley on top. Toss gently to combine. Taste and add more salt if needed.

Spoon into bowls and top with grated Parmesan if you like. Serve immediately while the orzo is still creamy.