Preheat the oven to 400°.
In a large bowl, combine the sugar, flour, cinnamon, and salt.
Add in the egg, butter, and vanilla. Mix well before adding in the milk and mixing again.
Pour every last bit into your unbaked pie crust.
Pop it into the oven and bake at 400° for about 15 minutes, and then reduce the heat to 350° and bake another 45 minutes. (Don’t forget to cover the crust with a pie crust shield the last 15-20 minutes. This will keep your crust from burning.)
Typically, you serve cinnamon cream pie cooled, but thankfully, it sets up quickly, and you can dig into it without it cooling completely. Warm cinnamon cream pie is divine and pairs quite nicely with a cup of coffee.