Preheat the oven to 350 degrees F (175 degrees C).
Fill a large pot with lightly salted water and bring to a boil over high heat. Stir in the macaroni, and cook uncovered, stirring occasionally, until the pasta has cooked through, but is still firm to the bite, about 8 minutes. Drain well.
Melt 1/4 cup butter in a large saucepan over medium heat. Stir in flour and salt. Cook, stirring constantly, for 2 minutes. Whisk in milk and simmer, stirring frequently, until mixture thickens slightly, about 5 minutes.
Turn off heat and stir in Cheddar cheese until the cheese is melted. Add the macaroni and stir to coat. Pour the mixture into a 9×13-inch baking dish. Mix the 1/4 remaining cup melted butter and crushed crackers together in a bowl; scatter the cracker mixture evenly over the macaroni mixture.
Bake in preheated oven until golden brown on top, about 45 minutes.