Preheat the oven to 375 degrees Fahrenheit. Butter a 10-inch springform pan, and set aside.
Cook the pasta to al dente according to the package instructions. *Be sure to salt the water!
2 pounds wide rigatoni pasta
In a saucepan over medium heat, melt the butter. Add the flour, and whisk to combine. Cook the mixture 2-3 minutes.
8 Tablespoons unsalted butter, 1/2 cup all-purpose flour
Gradually add the hot milk, whisking continuously until the sauce is smooth and thick. Add the remaining seasonings, stirring to combine.
5 cups whole milk, 3 teaspoons kosher salt + more or less to taste, 1/2 teaspoon cinnamon OR nutmeg, Optional: 1 teaspoon garlic powder, 1 1/2 teaspoons ground black pepper + more or less to taste
Remove the saucepan from the heat, and set it aside.
In the prepared springform pan, add 2 cups of the prepared sauce, spreading it out evenly.
Arrange the pasta right side up in the pan, packing it tightly.
Pour the remaining sauce evenly on top, and add the Mozzarella cheese.
2 cups Mozzarella cheese
Bake 30 minutes or until the top is golden brown.
Cool for 20 minutes before removing the rigatoni pie from the pan.
Slice, and enjoy!
Store covered in the refrigerator for up to 2 days.