Green Zebra tomatoes make a terrifically watermelon-green jam, but you can use any small or medium-sized tomato in this recipe. The result is a jam that tastes a little like ketchup and a lot like harvest time. Use Pomona’s Universal Pectin to set the jam. It’s available at natural food stores or online from the Greenfield, Massachusetts– based distributor (PomonaPectin.com).
Yield: 10 half-pints
10 half-pint jars with lids and bands
20 medium-sized heirloom tomatoes, whole
2 quarts water
1 cup kosher salt
1 large white or yellow onion
1 head garlic
2½ cups sugar
3 quarts apple cider vinegar
¾ tablespoon coriander seeds
¾ tablespoon yellow mustard seeds
1 teaspoon whole black peppercorns
2 bay leaves
4 teaspoons Pomona’s calcium water
4 teaspoons Pomona’s Universal Pectin
Place the tomatoes in a large glass or ceramic bowl or crock. Add 2 quarts water and 1 cup salt. Put a plate on top of the tomatoes to hold them down and soak them for 24 hours.
On the second day, drain and rinse the tomatoes. Cut the onion into quarters and halve the garlic cloves. Bring a ½ cup sugar, vinegar, onion, garlic, coriander, mustard, peppercorns and bay leaves to a boil, turn off the heat and steep for 15 minutes. Pour the hot brine through a strainer over the tomatoes. Cover with a plate and a cloth and soak for 24 hours.
On the third day, drain the brine and reserve. Crush the tomatoes in a food processor or by hand, yielding 6 cups of pulp. To this, add 2 cups of the reserved brine and calcium water. Bring to a boil, stirring regularly.
In a separate bowl, combine pectin into remaining sugar; mix well.
Once the tomatoes boil, add the sugar and pectin, stirring to combine. Return the mixture to a brief boil.
Pack the jam in half-pint jars, leaving ¼ inch headspace. Process the jars for 10 minutes in a hot water bath canner. You can keep this jam on your shelf for up to a year.
If you don’t want to process the jars in a canner, fill them with the very hot jam, seal them and then turn the jars on their heads for 3 minutes. The jars will still form a vacuum and seal. They can be kept refrigerated for 3–4 months.