01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Bring a large pot of salted water to a boil. Add cauliflower florets and cook for 4 minutes. Add pasta and cook both together for 5–6 minutes, until pasta is al dente and cauliflower is just tender. Drain and set aside.
03 - In a medium saucepan, melt butter over medium heat. Whisk in flour to form a roux; cook for 1–2 minutes until bubbling but not browned.
04 - Slowly whisk in milk, stirring constantly until thickened, about 4–5 minutes. Remove from heat. Stir in cheddar, mozzarella, Parmesan, garlic powder, onion powder, smoked paprika, salt, and pepper until smooth.
05 - Combine cooked pasta and cauliflower with the cheese sauce. Mix well and transfer to the prepared baking dish.
06 - In a small bowl, toss breadcrumbs with Parmesan and olive oil. Sprinkle evenly over the top of the pasta mixture.
07 - Bake for 20–25 minutes, or until bubbling and golden on top. Let rest 5 minutes before serving.