Add all the ingredients to a blender and blend until smooth. This may work best in a high-speed blender (like a Vita-Mix), but you can definitely make it in a regular blender. Just blend extra-long, or perhaps strain if you want it perfectly smooth.
Tiny bits of cashews won’t hurt anyone though!
If you’re making this sauce for pasta, drain the pasta and return it to the hot empty pan. Pour the sauce over, place on medium heat, and stir until heated through. Serve with lots of fresh cracked black pepper.