Preheat the oven to 400 degrees for baking the crisps.
In a medium sauce pan add the apples, brown sugar and lemon and cook over medium heat, stirring occasionally until the apples are softened and start to release their juice. About 7-8 minutes. If you want your apples a little firm, cook them less. If you want them really soft, cook them a little longer.
Add the cornstarch that you dissolved in the cold water and return to a simmer and cook until the liquid thickens--about 5 minutes or so. It's going to thicken a little more as it cools too. Set aside.
For the crisps
In a small bowl, mix the cinnamon and sugar.
Brush the tortillas with the melted butter and sprinkle with the cinnamon sugar. Bake 6 to 8 minutes until crisp and golden brown. Keep an eye on these--they'll brown fast.