Put a large pot of water to boil.
Heat the olive oil in a large skillet over med-high heat. Add the onion and cook until slightly softened. Add the garlic and cook, tossing regularly until onion is translucent.
Slowly add the vodka (especially be careful if cooking over an open flame). Simmer until liquid is reduced by ~2/3s. Reduce heat to medium-low. Also, during this time add the pasta and a handful of kosher salt to the pot of boiling water and cook pasta according to package directions.
Meanwhile, process the cashews plus 1/2 cup water in a food processor until very creamy smooth. Scrape down the sides of the bowl if necessary.
Add the cashew cream and the marinara to the onion mixture. Stir well and heat gently to warm through. Season well with salt and pepper to taste (will need a good amount of kosher salt, at least ~1/2 tsp).
Once pasta is done, drain and add to the sauce. Serve topped with parsley, additional fresh cracked pepper, and a little drizzle of olive oil.