Sterilize 6 half pint jars by heating your oven to 275 degrees. Place jars on a silicone mat on the rack of the oven. Allow jars to bake for at least 20 minutes. Remove jars when ready to fill with hot jelly. (Do not add cold food to hot jar or it could shatter). Cover your lids with boiling water for 5 minutes before ready to use.
Combine sugar, pepper, mango, apple, jalapeno, vinegar and butter in a large pot. Stir well.
Bring to a boil over medium heat. Boil for 10 minutes. Allow a teaspoon to cool. Taste for spiciness. Add more jalapeno if desired.
Add lemon juice and pectin. Bring to a boil and boil 1 minute.
Use tongs to transfer a couple of jars at a time from the oven to a heat proof mat. Ladle the hot jelly mixture into the jar leaving at least a ½" headspace. Insert a knife and loosely stir to remove any air bubbles. Position the lid and then screw on the rim to finger tight. Repeat with remaining jars and jelly. Jelly will set as the jars cool.
You have two choices at this point. Allow jars to cool to room temperature for 24 hours and refrigerate or freeze for up to 12 months.orSubmerge the jars on a rack in a canner or other deep cooking pot with a rack and a lid, Cover jars with 2 inches or water. Bring to a boil and simmer for 5 minutes. Remove jars with tongs and transfer to a heat proof mat. Allow to cool to for 24 hours to room temperature. Store in a cool, dark place. (5 minutes canning is for 0-1,000 feet above sea level. Add 1 minute of processing for each additional 1,000 feet additional altitude.)