Cook the pasta to al denté according to the package direction.
Reserve about ¼ cup of the pasta cooking water. When the pasta is al dente, drain but don't rinse. Return the pasta to the pot, cover and set aside.
Place the crawfish tails in a bowl and sprinkle with Creole seasoning. Mix well and set aside.
In a large sauté pan, melt the butter over medium-high heat until frothy.
Add the yellow onions and saute until soft, about 8 minutes.
Add the garlic and continue to saute until aromatic, about 2 minutes.
Add the creole seasoning and cayenne (if using) and stir well. Saute another two or three minutes.
Add the wine, bring to a heavy simmer and allow the wine to evaporate almost completely.
Add the cream and lemon juice, stirring and shaking the pan until well blended.
Simmer on low for a couple of minutes until it begins to slightly thicken.
Add the crawfish tails a few at a time and stir well to blend completely.
Allow the crawfish tails to only warm through (about 3 minutes), then add the green onions and parsley.
Mix well and simmer about two minutes.
Add the reserved pasta water and a drizzle of olive oil to the cooked pasta and stir thoroughly.
Add the cooked pasta to the sauce a little at a time. Stir completely to combine the pasta, sauce and crawfish tails before adding more pasta. See Recipe Notes about how much pasta to add.
When the pasta has been thoroughly combined, stir in about ½ cup of the Parmesan cheese and mix well. Reserve the remaining parmesan cheese to add at the table.
Remove from the heat. When serving, sprinkle more parmesan cheese on top.