Coarse salt and ground pepper
12 ounces spaghetti
1 pound large (31 to 35) peeled and deveined frozen shrimp, tails on (if desired), thawed
3 tablespoons olive oil
2 garlic cloves, minced
2 tablespoons coarsely chopped fresh rosemary
1/4 teaspoon red-pepper flakes
1 tablespoon fresh lemon juice
1. In a large pot of boiling salted water, cook spaghetti until al dente; reserve 1/2 cup pasta water. Add shrimp to pot, and stir. Immediately drain spaghetti and shrimp, and set aside (the shrimp will continue to cook).
2. In same pot, heat oil over medium. Add garlic, rosemary, and red-pepper flakes. Cook, stirring, until garlic is golden, 1 to 3 minutes.
3. Remove from heat; return pasta and shrimp to pot. Add lemon juice and enough pasta water to create a thin sauce that coats pasta. Season with salt and pepper, and serve.