Bring a large pot of salted water to boil. Add your pasta of choice and cook according to package instructions.
While the pasta cooks, transfer your cashews, roasted peppers, garlic, onion powder, nutritional yeast, miso, lemon, salt, and pepper to a blender, along with 1/3 cup water. Blend till smooth, adding a tablespoon or two of extra water if the sauce is overly thick or difficult to blend (it should be about the texture of an alfredo sauce). Taste sauce and add salt and pepper as desired.
When the pasta is ready, drain it and fold in your sauce (you may not use all of it; if you have some leftover, it can be thinned and used as a salad dressing!). Divide pasta onto plates and top as desired. Serve.
Notes
Leftover sauce will keep for up to 5 days in an airtight container in the fridge.