In a blender, combine the vinegar and peppers, and pulse until the peppers are finely chopped, speckled throughout the liquid. Transfer to a medium saucepan, and add the sugar and salt. Bring to a boil over medium-high heat and let cook until the sugar fully dissolves, 5 minutes.
Sprinkle the pectin over the mixture and continue to cook until fully incorporated, 1 to 2 minutes more.
Divide the jelly between 2 sterilized mason jars, pressing the mixture down until there is only about ½ inch of space left at the top of each jar. Wipe the rim then affix the lid on each jar.
Bring a stockpot filled with enough water for the jars to be completely submerged to a boil. Arrange the jars on a wire rack and lower into the water. Boil for about 15 minutes.
Carefully remove the jars and let them cool to room temperature on a folded towel, making sure not to disturb the lids. Check the seal after 24 hours; it should not flex when pressed in the center. The jelly will keep for up to 1 year.