1/2 pound rock shrimp or peeled and deveined medium shrimp
6 tablespoons unsalted butter, cubed
Freshly ground pepper
Finely grated bottarga, preferably mullet, for sprinkling (optional; see Note)
In a large saucepan of salted boiling water, cook the pasta until al dente.
Meanwhile, scoop 1/4 cup of the pasta cooking water into a large, deep skillet. Add the lemon juice and zest. Arrange the shrimp and butter in the skillet in an even layer and season lightly with salt and pepper. Bring to a simmer over moderate heat and cook, stirring gently, until the butter is melted and the shrimp are nearly cooked through, 4 minutes.
Drain the pasta, reserving another 1/4 cup of the cooking water; add the pasta to the skillet. Cook over moderate heat, tossing and adding some of the reserved cooking water if needed, until the pasta is well coated and the shrimp are white throughout, 1 minute. Season with salt and pepper. Transfer to bowls, grate bottarga over the top and serve.