Bring a large pot of generously salted water to a boil. Add the macaroni and cook it until just shy of al dente, about a minute less than the package directs. Scoop out 1 cup of the pasta water and set it aside, then drain the pasta and return it to the pot.

While the pasta cooks, put the raw cashews in a small saucepan, cover them with water, and simmer for 10 minutes until they're soft all the way through, then drain them well.

Transfer the drained cashews to a blender and add the oat milk, nutritional yeast, Dijon mustard, onion powder, garlic powder, salt, and turmeric. Blend on high for 60 to 90 seconds, scraping down the sides once, until the sauce is completely smooth. Rub a little between your fingers, if you feel any grit, blend it longer.

Stir the lemon juice into the sauce, then pour the sauce over the drained pasta in the pot. Warm it over medium-low heat, stirring constantly, for 2 to 3 minutes until the sauce thickens and clings to the noodles. Loosen it with splashes of the reserved pasta water if it gets too thick.

Taste, add more salt if it needs it, and finish with a few cracks of black pepper. Serve warm, straight from the pot.