In a high-speed blender, combine the cashews and water and blend for 1 minute until smooth.
Steam the cauliflower florets and drain off any liquid. Add to the blender along with 1 clove of garlic, nutritional yeast, Italian seasoning, salt and pepper. Blend on high for 1 minute until combined and smooth.
Cook the pasta according to the directions on the package. Drain and set aside.
In a medium saute pan, add the olive oil over medium heat. Mince the remaining garlic clove and add to the hot oil. Saute for 30 seconds, then pour in the sauce from the blender. Mix well with a spatula and let cook on medium heat about 5 minutes--it should be lightly bubbling, stir frequently. Add in the pesto and red pepper flakes, if using. Stir well to combine and let cook for another 5 minutes to fully combine and thicken.
Toss the cooked pasta into the sauce and stir well to fully coat. Enjoy!