Make a brine with 3 cups white vinegar, 1½ cups of sugar, cinnamon stick, a few cloves, allspice berries and peppercorns. Add 2 bay leaves and a small dried chili, then bring it all to a boil in a 4-quart non-reactive saucepan.
Simmer the onion rings, in three separate batches (that means, one-third of the onion rings at a time), for 20 seconds each (20 seconds for each batch) in the brine. Remove onions to a baking sheet using a slotted spoon to drain them, and let cool.
Then you do it again, simmer the onions in three separate batches, for 20 seconds each. Drain them, and cool.
Then you do it again…simmer the onions in three separate batches (yes, have you memorized it yet?… 20 seconds each…then drain them and let them cool.)
Finally you chill the brine thoroughly. Once chilled, add the onions and store in the refrigerator.