Preheat the oven to 325 degrees F (165 degrees C). Grease a 2-quart baking dish.
Place a steamer insert into a saucepan and fill with water to just below the bottom of the steamer. Bring to a boil. Add cauliflower; cover and steam until crisp-tender, about 5 minutes. Drain and set aside.
Combine sour cream, Cheddar cheese, cornflakes, bell peppers, and salt in a medium bowl. Stir in steamed cauliflower, then transfer to the prepared baking dish. Sprinkle with Parmesan cheese and paprika.
Bake uncovered in the preheated oven until heated through, 30 to 35 minutes.