Prepare your jars by sterilizing them in boiling water.
Chop the bell peppers finely and set aside.
In a large pot, combine the chopped peppers and apple cider vinegar.
Bring the mixture to a boil over medium heat.
Add the fruit pectin and stir well.
Once boiling, add the sugar all at once and stir to dissolve.
Bring to a rolling boil again and cook for 1 minute.
Remove from heat and skim off any foam.
Add red pepper flakes and lemon juice, stirring to combine.
Pour the hot jelly into sterilized jars and seal immediately.