1/2 cup cashews, soaked in 1 cup water for at least 30 minutes. Soaking allows them to blend easier.
1/2 cup water
12 oz. penne pasta
In a large saute pan, heat the butter over medium heat. Add onions, and garlic; cook down until soft and onions are translucent. Stir in red pepper flakes and salt. Add crushed tomatoes, reduce heat to medium-low and cook for 25 minutes stirring occasionally. Add vodka to the sauce and cook an additional 5 minutes until alcohol is cooked off.
Bring a large pot of water to a boil.
Add the soaked and drained cashews to a blender or food processor. Add 1/2 cup of water and blend until a smooth sauce forms, about 2 minutes depending on the power of your blender. Pour the cream into the tomato sauce, stir to mix and reduce heat to low.
Add the pasta to the water and cook until al dente. Drain the pasta and reserve 1/2 cup of pasta water. In a large bowl, toss together the cooked pasta, sauce, and reserved pasta water.