Cook pasta according to package directions, about 9 minutes; add broccolini and red pepper during last 2 minutes of cooking. Reserve 1/2 cup cooking water. Drain.
Meanwhile, heat 1 tbsp each of the oil and butter in large stainless skillet over medium-high heat. Coat scallops with flour and season with 1/4 tsp each of the salt and pepper. Sauté 2 minutes per side; reserve. Add remaining tbsp oil and butter to skillet and cook garlic 30 seconds. Combine cornstarch and broth; add to skillet and simmer 1 minute.
Add pasta, parsley, lemon juice, remaining 1/2 tsp salt, remaining 1/4 tsp pepper and scallops. Toss gently to combine and simmer 1 minute. Add some of the reserved cooking water if needed.
Spoon into a large serving bowl. Sprinkle with Parmesan.