1 pound (454 g) Tropea or other red onions, cut into small dice
2 C. (400 g) sugar
1 C. (237 g) Sangiovese or other sturdy red wine
1/2 to 3/4 tsp. kosher or fine sea salt
10 whole peppercorns
1 whole clove
1 bay leaf
1-inch piece vanilla bean
1/2 cinnamon stick
2 T. red wine vinegar

4-inch square of cheesecloth and a length of kitchen twine
Instant-read thermometer (optional)
2 sterilized 1/2-pint jars and 1 sterilized 4-oz. jar, and their lids
Basic water-bath canning equipment

Combine the onions, sugar, wine, and salt in a wide, heavy-bottomed saucepan. Use the cheesecloth to make a sachet for the peppercorns, clove, bay leaf, vanilla bean, and cinnamon stick and tie it up with the kitchen twine. Put the sachet in the pot with the other ingredients. Bring the onion mixture to a boil over medium heat, stirring to dissolve the sugar. Cook at a simmer, stirring often, until the jam has thickened and reaches 220 to 225°F and you can drag a path along the bottom of the pot with a silicone spatula, about 20 minutes. Stir in the vinegar and remove from the heat. 3 • Ladle the jam into jars, leaving 1/4 inch headspace. Wipe the rims with a clean, damp cloth, if necessary, and screw the lids on the jars. Process in a boiling-water bath for 10 minutes. Remove the jars and set them upright on a clean kitchen towel. Let cool to room temperature before storing in a cool, dark place for up to 1 year. Refrigerate once opened, and use within 6 months. If any jars have failed to seal properly, store them in the refrigerator and enjoy those first.