Fill a boiling-water canner about 2/3 rds full with water and bring it to a boil.

In a large pot, bring 8 cups of water to a boil, add sliced onions and cook for 4 minutes.

Drain onions and set aside.

In a large pot bring apple cider vinegar, sugar, water and salt to a boil, stirring until the sugar and salt has completely dissolved.

Add onions to brine mixture, stir and then remove from heat.

Ladle the onions and brine mixture into hot prepared jars, filling to within 1/2 inch of the tops.

Wipe the jar rims and threads clean if needed. Cover with 2-piece lids. Screw bands tightly. Place jars on elevated rack in canner and then lower the rack into canner. Make sure the water is covering the jars by at least 2 inches. Place the lid on the pot and bring the water to a boil.

Process the pickled onions for 10 minutes. One recipe makes {4} pint jars

Remove jars and place on a towel to cool. After 24 hours check the seals. If the lid springs back, onions are not sealed and refrigeration is necessary.