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. Spread half the shredded cheese on top. Repeat the whole process for a second layer of noodles, salt, butter, and cheese.
Pour milk over the layers of mac and cheese, only enough to fill the baking dish a third of the way full.
Bake the mac and cheese in the oven 30 minutes, uncovered. It should be bubbly and slightly browned when done. Cool slightly before serving.