Cook pasta al dente according to package directions – drain in a colander and return to the pan.
To make Alfredo sauce: Put about 1” water in a medium pan, add cauliflower and bring to boil. Lower heat, cover and simmer about 10 minutes until cauliflower is fork tender. Add more water if necessary so cauliflower doesn’t burn. Drain.
In a blender, add cauliflower, water, cashews, lemon juice, nutritional yeast and salt. Puree until smooth and creamy. Add more water if needed to get the right consistency.
Add vegetables and alfredo sauce to the pasta, mix well and heat through. Garnish with chopped parsley or cilantro.