Cook the Apples: In a large stockpot, combine the diced apples, water, and butter. Cook and stir over low heat until the apples are tender (about 10 minutes).
Add Pectin: Stir in the pectin and bring to a rolling boil, stirring constantly.
Add Sugars and Spices: Add the granulated sugar, brown sugar, cinnamon, and nutmeg. Return to a rolling boil and boil for 1 minute, stirring constantly.
Prepare Jars: Remove from heat and skim off any foam. Carefully ladle the hot mixture into hot half-pint or pint jars, leaving a 1/4-inch headspace. Remove air bubbles, wipe rims, and adjust lids.
Process Jars: Process jars for 10 minutes in a boiling water bath.
Cool and Store: After processing, twist jars gently from side to side while cooling (after the lid has sealed) to evenly distribute apple pieces throughout the jam.
Notes
Ensure your jars are sterilized before filling with jam.
You can adjust the amount of cinnamon and nutmeg to taste if you prefer a stronger spice flavor.