Fill a large skillet about two-thirds full with water. Add the salt and bring to a rolling boil over medium-high heat.

Add the elbow macaroni, turn the heat to medium, and cook, stirring occasionally, until just shy of al dente (about 10 minutes).

Drain the macaroni well, returning it to the skillet. Turn the heat to low. Add the butter and stir until melted.

Pour in the evaporated milk, Dijon mustard, and cayenne pepper. Stir to combine.

Add the shredded sharp cheddar cheese in three batches, stirring frequently until each batch is melted before adding the next. Continue stirring for about 5 minutes total, until the sauce is smooth and thick.