In a large pot with boiling salted water cook fettuccini pasta until al dente. Drain. Stir in pesto sauce and 2 tablespoons of olive oil.
Meanwhile, in a large skillet, saute onion and garlic in 3 tablespoons olive oil until soft. Add green bell pepper, mushrooms and cook until soft, about 3 minutes. Stir in dry white wine, lemon juice, salt and pepper to taste, and bring to a boil. Add scallops and toss for 2 minutes. Take care not to overcook the scallops, as they will toughen when exposed to prolonged heat.
Toss the pesto covered pasta with the scallop sauce. Sprinkle with grated Parmesan cheese. Serve immediately.
