Preheat oven to 400°F. Butter an 8x8-inch glass baking dish.
Layer half the precooked noodles into the buttered dish. Sprinkle with half the salt. Cut half the butter into small chunks and scatter the chunks over the salted noodles. Place half the shredded cheese on top of this, and repeat the whole process for a second layer of noodles, salt, butter, and cheese.
Pour the milk over the layers of mac and cheese, but do not use more milk than will fill your baking dish a third of the way full.
Bake the mac and cheese in the oven for about 30 minutes, uncovered. It should be bubbly and slightly browned when it is done.