easier option—running the jar and lid through the dishwasher. The
jar should be warm when you fill it.
To prepare the vegetables, use the julienne blade on a mandoline
slicer and create a kind of radish-onion relish or simply slice the
radishes and onions very thin into rounds and rings. Whichever
method you choose, fill the jar alternating between the radishes
and the onions, so you see separate layers of black and green. Pack
the layers tightly.
In a pot, combine the vinegar, sugar, water, and salt and taste it
for balance. (Does it need more vinegar? More sugar?) Bring to a
boil over high heat and then pour over the vegetables in the jar,
leaving room at the very top for a vacuum to form. Seal with the
lid.
Put the jar right into the refrigerator; as it sits, it will get more
and more intense. It won’t be shelf-stable*, though, and will only
last a few weeks.
* If you think you’ll eat these pickles, or any pickles you make,
over the course of 1 or 2 weeks, you can skip the jar and just
use a clean bowl. Simply cover with plastic wrap and store in
the refrigerator.* If you want to put up these pickles so they last for months,
create a “shelf” at the bottom of a pot (you can make one with
aluminum foil) for the jar to rest on (the bottom of the jar
should not touch the bottom of the pot). Fill the pot with water
and bring it to a boil. Place the filled, sealed jar on the shelf and