Using a zester, cut peel (colored part only) from lemon in fine shreds (or use a vegetable peeler to pare off colored part of peel, then cut peel into fine slivers). Set lemon peel aside. In a large pan, cook pasta in about 3 quarts of boiing salted water until tender to bite (8 to 10 minutes). Drain, rinse with cold water, and drain again; set aside. Rinse scallops and pat dry; if using sea scallops, cut into 1/4 inch thick slices. Set aside. Melt butter in oil in a wide frying pan over medium-high heat. Add bell peppers, garlic, and red pepper flakes; cook, stirring, for one minute. Add broth and lemon juice to pan; bring to boil. Add scallops, cover and cook until opaque in center; cut to test (about 3 minutes). Remove from heat. Lift scallops and peppers from pan with a slotted spoon and set aside. Add pasta to pan juices; lift and mix with 2 forks until pasta is hot. Pour pasta and sauce into serving dish. Top with scallops and peppers; then sprinkle with parsley and lemon peel. Season to taste with salt and pepper. Before serving, mix lightly with a serving fork and spoon. Make 4 to 6 servings.