Combine the apples, red bell pepper, jalapeños, apple cider vinegar, honey, salt, and cinnamon (if using) in a large saucepan. Stir well so everything mixes.

Bring the mixture to a boil over medium-high heat, stirring frequently; you'll hear a steady simmer that becomes a lively bubble.

Stir in the powdered pectin and return to a rolling boil for 1 minute so the pectin dissolves and activates.

Immediately add the sugar all at once, stirring constantly so it melts into the hot mixture. The pot will look glossy.

Bring back to a full rolling boil and boil hard for 2 minutes, stirring continuously; look for the jam to thicken and the surface to show small, fast bubbles.

Remove from heat and skim off any foam with a spoon; the jam should look clear and thickening at the edges.

Carefully ladle hot jam into sterilized jars, leaving about 1/4-inch headspace, then wipe rims clean.

Seal jars and process in a boiling water bath for 10 minutes, or let cool and refrigerate if not canning.