Preheat the oven to 450. Roll the pie crust out for a 9" pie pan and put it in the pan.
In a blender or food processor or mixer, blend the cottage cheese until creamy and smooth. Put it in a mixing bowl, if it's not already there, and add the flour, sugar, salt, and eggs. Mix until smooth. Add the milk and stir it in slowly.
Pour the custard into the pie shell and sprinkle with cinnamon. It has a good chance of boiling over so if you have one of those pie drip pans this is the time to use it! I like to pull the oven rack partially out, put the unfilled pie down on top of the drip pan, then pour in the custard.
Bake for 10 minutes, then reduce the heat to 300 and bake at least another hour. I baked mine another hour and 15 minutes and it was still pretty wobbly in the middle but it did firm up as it cooled.