1. Cut asparagus into 1-inch pieces. Cook in boiling water for 30 seconds. Plunge into ice water to stop the cooking process; drain and set aside.
2. Bring a large pot of water to a boil.
3. Sauté asparagus, shrimp, bell pepper, and, if desired, dried crushed red pepper flakes in hot oil in a large skillet over medium-high heat 5 to 7 minutes or until shrimp are cooked and vegetables are tender. Reduce heat to medium-low; stir in half-and-half and salt. Cook, stirring occasionally, until thoroughly heated.
4. Cook angel hair in boiling water according to package directions; drain and return to pot. Add shrimp mixture, lemon rind, and lemon juice to hot pasta; toss. Transfer to a serving platter; sprinkle evenly with cheese. Serve immediately.