Creating this amazing apple pie filling is straightforward if you follow these simple steps:

1. Prepare the Apples: Peel, core, and slice the apples into thin wedges. Make sure to cut them evenly for consistent cooking.
2. Toss with Lemon Juice: In a large mixing bowl, combine the sliced apples with lemon juice to prevent browning.
3. Mix the Dry Ingredients: In a separate bowl, mix the sugar, cinnamon, nutmeg, salt, and cornstarch until well combined.
4. Combine Mixtures: Pour the dry mixture over the apples. Toss until the apples are evenly coated with the sugar and spice mixture.
5. Cook the Filling: In a large saucepan, bring water or apple cider to a simmer over medium heat. Add the apple mixture and cook for about 20-30 minutes until the apples are tender and the mixture thickens. Stir occasionally to prevent sticking.
6. Add Vanilla: If you are using vanilla extract, stir it in just before removing the filling from the heat.
7. Cool: Once done, remove from heat and let it cool before using. This filling can be stored in airtight containers in the refrigerator for up to a week or frozen for extended use.

With these straightforward instructions, you will master the art of making your own apple pie filling in no time.