Bring a large pot of salted water to boil and cook the pasta until al dente-- firm but tender.
Place the canned plum tomatoes in a bowl and squish them with your fingers to break them down. Set aside.
Blend the cashews with ½ cup of water until very smooth. Set aside.
While the pasta is cooking, heat the oil in a large saucepan. Add the garlic followed by the onions. Season with salt and pepper, and cook until the onions have softened, about 5 minutes.
Add the vodka to the pot and mix. When the moisture has evaporated, add the oregano and red pepper flakes.
Stir in the tomatoes and add a cup of water. Mix, bring the sauce to a boil, then turn down the heat and let it continue to simmer for 10 minutes.
Stir in the cashew cream and let it all warm through.
Drain the cooked pasta and mix it into the sauce. Check seasoning and add salt and pepper as needed. Garnish, if you wish, with fresh parsley or oregano.