Mix cornstarch with 1/4 cup of water.
Heat up a large pan, add the apples, butter, sugar and ¼ tsp salt, ground cinnamon and a few pinches of grated nutmeg. Cook for 4 minutes. See the liquid on the bottom of the pan. Now add the cornstarch slurry. Add about ¾ cup of water and bring this up to a boil. Once it boils, cook for just 1 minute. Turn the heat off and put aside to cool completely. The sauce will thicken as it sits.