Step 1: Harvest the grapes or buy from the local market (they are in season now!). 4-5 cups are needed for a 9-10 inch pie.
Step 2: A little labor intensive, but each grape has a seed inside that must be removed. Squeeze the grape so the inside pops out into a bowl, and put grape the skin in another bowl.
Step 3: Heat the insides with the seeds in a skillet until they turn pale yellow and the seeds become loose. Push the insides through a fine strainer or food mill to separate the seeds from the juice and pulp.
Step 4: Combine strained juice/pulp with skins, 1 cup sugar, 1 T lemon juice, 3 T cornstarch and stir until smooth. Pour into an unbaked pie crust (homemade crust is worth it!), dot with butter pats, and cover. Cut vents. Sprinkle crust with sugar and cinnamon (the cinnamon is key for the perfect flavor). Bake at 450 degrees for 30 mins, then 375 degrees for 30 mins until bubbling through the vents.
Step Five: Enjoy this slice of heaven with a little vanilla ice cream!