Place raw cashews in a small bowl, cover with room-temperature water by at least 1 inch, and soak for 30 minutes to 4 hours (or 15 minutes in boiling water if short on time). Drain through a fine mesh strainer, rinse under cold water, and discard the soaking liquid.
Bring a large pot of generously salted water to a rolling boil, add the elbow macaroni, and cook until al dente according to package directions. Before draining, reserve ½ cup (120ml) of starchy pasta water, then drain through a colander without rinsing.
Add drained cashews, plant-based milk, water, nutritional yeast, garlic powder, onion powder, dry mustard, smoked paprika, turmeric, lemon juice, white miso paste, salt, and black pepper to a high-powered blender. Blend on high for 60 to 90 seconds until completely smooth and creamy, scraping down the sides as needed.
Pour the blended cashew sauce into a medium saucepan and warm over medium-low heat, stirring frequently, for 3 to 4 minutes until hot and slightly thickened. Do not let it boil; if the sauce is too thick, stir in reserved pasta water one tablespoon at a time.
Add the drained pasta to the saucepan and toss to coat every piece evenly in the sauce. Let sit over very low heat for 1 minute, then taste and adjust salt and pepper as needed.
Serve immediately in bowls, drizzled with olive oil and garnished with a sprinkle of smoked paprika, fresh parsley or chives, toasted panko breadcrumbs, and red pepper flakes as desired. Enjoy right away for peak creaminess.