- Cook pasta in a large pot of boiling water until al dente; drain.
- Meanwhile, melt butter in a large saucepan.
- Saute onion and garlic over medium heat until tender.
- Add shrimp; saute over high heat for 1 minute, stirring constantly.
- Stir in half-and-half.
- Cook, stirring constantly, until sauce thickens.
- Place pasta in a serving dish, and cover with shrimp sauce.
- Sprinkle with black pepper and parmesan cheese.
- Garnish with parsley and lemon slices.