Preheat the oven to 375°F and lightly grease a 9 × 13-inch baking dish with vegan butter.
Place the raw cashews in a heatproof bowl and cover them with boiling water. Let them soak for about 10 minutes to soften. For an especially smooth sauce, soak them for 1–2 hours if you have extra time.
While the cashews soak, bring a large pot of salted water to a boil. Cook the macaroni according to the package directions until just tender, being careful not to overcook it. Drain well and set aside.
Drain the cashews and add them to a high-speed blender along with the hot water, lemon juice, nutritional yeast, Dijon mustard, garlic powder, onion powder, smoked paprika, salt, and black pepper.
Blend on high until the sauce is completely smooth and creamy. Scrape down the sides as needed and blend again until there are no visible pieces of cashew remaining.
Pour the creamy sauce into a saucepan and warm it over medium-low heat for 3–4 minutes, stirring frequently. The sauce should become slightly thicker but remain pourable.
Add the cooked macaroni to the sauce and gently stir until every noodle is evenly coated.
Transfer the creamy macaroni to the prepared baking dish and spread it into an even layer.
Combine the panko breadcrumbs, melted vegan butter, smoked paprika, nutritional yeast, and a pinch of salt in a small bowl. Stir until the breadcrumbs are evenly coated.
Sprinkle the breadcrumb mixture evenly over the macaroni.
Bake uncovered for 15–20 minutes, until the sauce is bubbling around the edges and the breadcrumb topping is crisp and golden.
Let the mac and cheese rest for about 5 minutes before serving. This gives the sauce a chance to settle while keeping the dish creamy and scoopable.