Bring the water and (optional) salt to a boil in a 2-quart saucepan. Stir in macaroni and simmer until tender, about 8 minutes. Transfer macaroni to a colander to drain.

Meanwhile, simmer the hot dogs in a medium saucepan until heated through, about 5 minutes. Or grill them or cook in a ridged grill pan over medium heat for 5 minutes, turning frequently.

Stack the cheese and cut into small cubes. Place the milk in a saucepan along with the cheese and (optional) cayenne pepper. Cook over medium heat stirring often just until cheese is melted and mixture slightly thickens, about 3 minutes. Stir in the cooked macaroni and keep warm over low heat. The mac and cheese will become thicker during this time.

Place the hot dogs in the hot dog buns and top with the mac and cheese. Sprinkle the parmesan cheese over the mac cheese if desired.