Cook the pasta in salted water until al dente, about 10 minutes (or according to the package instructions). Reserve 1½ cups of pasta water before draining. While the pasta is cooking, make your sauce.
Make the Sauce
To a large pan or skillet, add the olive oil and chili flakes and heat over medium heat. Add the onion and cook until translucent, about 3-4 minutes. Add the garlic and cook for 30 seconds. Remove from heat and add to a blender.
Drain and rinse the cashews. Add them to the blender with the remaining sauce ingredients. Start with ½ cup of water and increase until you have a smooth consistency.
Cook the Asparagus and Bring it All Together
Heat the olive oil in the same pan as the garlic and onions and cook the asparagus for about 3-4 minutes, then add the spinach and cooked pasta.
Add in the sauce and toss to combine. If the sauce is too thick, loosen it with the reserved pasta water.
Taste test and adjust the seasoning accordingly, then transfer to bowls and finish with more vegan cheese, a drizzle of olive oil, and a pinch of chili flakes.