In a saucepan over medium heat, add cherries, granulated sugar, lemon juice, cornstarch, and cinnamon. Stir to combine.
Bring to a boil. Reduce heat to medium-low and cook for 8-10 minutes, or until mixture has thickened (if fruit looks dry, add a splash of water and turn down the heat slightly). Remove from heat and allow to cool slightly.
Baking Into A Pie
Preheat oven to 375 degrees. Place prepared pie crust into an 8 or 9 inch pie pan. Fill with cherry pie filling, then place top pie crust over filling. Pinch the edges closed, then make a slit in the middle of the pie for steam to escape. Optionally, sprinkle with sugar before baking.
Bake for 50 minutes, then remove from oven to cool.
Pie filling can be frozen for up to 3 months in a sealed, freezer safe container. Thaw in the refrigerator overnight before using.
Pie filling can be made with fresh or frozen cherries. If frozen, thaw them before beginning.