Bring a small-to-medium pot of very well-salted water to a boil and add your dried pasta. Cook it until firm tender, then drain.
Return pot to stove and melt butter in the bottom. Using a spoon or whisk, add flour and mix until it disappears.
Add milk, a tiny splash at a time, stirring constantly so no lumps form. Season with ¼ teaspoon kosher salt and many grinds of black pepper.
Bring sauce to a simmer. Cook, stirring, for 1 to 2 minutes.
Remove from heat and stir in grated cheese until combined.
Add drained pasta, stir to evenly coat.
Scoop into a bowl and finish it with more black pepper, if you wish.