Bring 5 cups water and salt to a boil in a heavy Dutch oven; gradually stir in grits. Return to a boil; reduce heat, and cook 4 to 5 minutes, stirring occasionally.
Stir in hominy, butter, and Cheddar cheese; spoon into a lightly greased 13- x 9-inch baking dish. Sprinkle with Parmesan cheese.
Bake at 350° for 45 minutes or until set.