Tomatoes are fruit, so why not make them into jam? Tomato jam will delight and surprise your friends with its palate-tickling balance of sweet and savory, and intense tomato flavor. It is the king of savory jams.
By far the best tomato for this recipe is the Early Girl. It has a robust flavor and excellent balance of sweetness and acidity. Other paste tomatoes like plum work well, as would many sweeter cherry tomatoes. Avoid the larger, waterier, blander heirlooms, no matter how beautiful they look.
It is possible to reach the gel point without adding pectin, especially if you leave the seeds and skins in.
Fill your canning pot with enough water to cover jars by an inch. Prepare your jars and lids, and sterilize the jars while preparing the jam.
Combine the tomato puree, sugar, lemon juice, salt, and nutmeg in a wide, nonreactive pan. Cook on medium heat, stirring frequently until the sugar is completely dissolved. Increase the heat to medium-high and bring to a boil. Add the homemade pectin.
Boil vigorously, stirring occasionally to prevent scorching, until the jam reaches the gel point. Remove from the heat.
Working swiftly, ladle the jam into sterilized jars and process via the standard water bath canning method for 10 minutes. Remove the jars to a rack or towel to cool, and leave undisturbed for 24 hours. Store sealed jars in a cool, dark space for up to a year. If any jars did not seal, refrigerate and use within 3 months.