Preheat the oven to 350 degrees F (175 degrees C). Spray a casserole dish with non-stick cooking spray.
Bring a pot of lightly salted water to a boil. Add cauliflower and boil until crisp-tender, about 5 minutes. Drain and place into the bottom of the prepared casserole dish.
Blend together Cheddar cheese, cottage cheese, ground mustard, garlic powder, onion powder, and salt in an electric blender until smooth.
Pour blended mixture over cauliflower and stir until completely coated.
Bake in the preheated oven until golden and bubbly, about 35 minutes.
