Preheat the oven to 350 degrees F. Butter the bottom of a baking sheet.
Bring a large pot of salted water to a boil. Add the macaroni and cook until tender, about 8 minutes; drain well. Transfer the macaroni to a large bowl, add the butter and toss to coat.
Whisk together the milk, eggs and 2 teaspoons salt in a medium bowl. Add the milk-egg mixture to the macaroni; add the Cheddar and stir until evenly distributed.
Pour the macaroni onto the prepared baking sheet and spread flat. Bake until the top is brown and bubbling, 20 to 25 minutes.