Cook the puff pastry shells according to package instructions and set aside.
Bring a large pot of water to a boil over high heat. Drop the linguine into the pot of boiling water and add a big pinch of salt. Cook according to package directions until the pasta is just tender. Save 1 cup cooking water and drain the pasta.
In a large skillet over medium heat, melt the butter. Add the onions and cook until they are soft, about 3 minutes. Do not let them brown. Add the wine and cook until most of the liquid has evaporated, about 5 minutes. Add the Alfredo sauce and lemon zest, bring to a simmer, turn the heat to low and cook for 2 to 3 minutes. Add the lemon juice and stir. Add the pasta to the skillet and toss it well to coat with the sauce. Add some of the cooking water if the sauce is too thick.
Remove the centers of each puff pastry shell. Place onto a plate and fill with the linguini, letting it spill over onto the plate. Garnish with the cheese and parsley.