Bring a large pot of water to a boil and add salt. Add the pasta and cook until al dente, about 12 minutes. While the pasta water comes to a boil, begin cooking the pan stew. Heat the olive oil in a large saute pan over medium-high heat until hot. Add the onions, reduce the heat to medium, and cook until light brown, about 3 minutes. Remove to a plate and reserve. Add the scallops, and cook without moving them until they brown on one side, about 1 minute. Turn and cook just until cooked through, about 1-1/2 minutes longer. (The timing will vary according to the size of the scallops. Bay scallops require only seconds.) Remove the scallops to a plate. Add the garlic to the pan and sauti briefly until light brown. Add the wine and bring to a boil, while stirring and scraping all over the bottom of the pan to loosen any browned bits. Add the stock, return to a boil, season with salt and pepper, and add the reserved onions. Simmer gently until the onions are tender, about 10 minutes. Add the peas and continue to cook until just tender, about 3 minutes. Return the scallops to the pan with the basil, lemon zest, parsley, and the butter, if using. Cook just until the scallops are warm. When the pasta is cooked, drain well and add to the sauti pan with the pea mixture. Taste for seasoning and serve immediately. | 
