Prepare jars and lids by them washing in hot water. Allow to drain dry.
Wash the peppers.
When preparing hot peppers, wear gloves. Using a paring knife, remove stems and seeds from peppers. This should render about 6.5 lbs. Using gloves is important with hot peppers! Keep your hands AWAY from your eyes.
Peel and chop onions and peppers into pieces that will fit your food processor or food grinder. Grind onions and peppers into a large bowl. Mix thoroughly (it will look like Christmas in a bowl!) Add salt. Cover and allow to sit overnight or for 3 hours to allow the salt to pull out any bitterness.
Using the fine mesh strainer, drain the mixture. Add to the pot the vinegar, sugar, mustard, and paprika. Bring to a boil. Reduce the heat and simmer uncovered for about an hour, stirring occasionally. It will thicken slightly.
While the relish is cooking, fill a canning kettle about 2/3 full with hot water. Bring to a boil. Fill clean jars with prepared relish.
Wipe the rims, add the lids, and screw on the covers "fingertip" tight.
Add filled jars to a canning rack and gently lower into canning kettle and bring back to a boil for 12 mins. Remove jars carefully and place them on a bath towel. Wrap with a second towel to allow them to cool gently.