Grandma McCorkle's Sugar Pie

Please don't confuse this with Sugar Cream Pie.

In a 2-cup measuring cup, combine ¼ cup flour & ¾ cup sugar. Stir to mix. Add water, stirring to mix, until you fill to the 2-cup mark. Pour into an unbaked pie shell. Dot with butter; sprinkle with cinnamon. Bake at 350 degrees until filling sets. The top will still be a little runny, but will firm as it cools.