TOMATO JAM

Steps:

• Toss tomatoes, sugar and salt together in a large, heavy bottomed pot. Let sit at least 15 minutes or up to overnight, tossing to coat periodically to dissolve the sugar. (This helps coax the juices out of the tomatoes.)
• Place a small plate in the refrigerator to chill. (You'll use this later.)
• Add the vinegar to the tomatoes, and bring to a strong simmer over medium heat until the skins burst and the juices start to boil, about 10 minutes. Add in any of the optional ingredients (see note), if using.
• Increase the heat to medium-high, and cook the jam. Using a wooden spoon or spatula, stir the jam, occasionally at first and more frequently as the juices thicken. Do this until most of the liquid has evaporated and the tomatoes have begun to break down, and the mixture resembles a very thick, shiny tomato sauce, 35 to 45 minutes. This is the stage at which it's most important to stir constantly along the bottom of the pot to prevent scorching and sticking. (Sugar is heavier than water and will concentrate at the bottom of the pot, increasing the chance that the fruit will burn.) How much the tomatoes break down will depend on their type and how ripe they are: For example, firm green tomatoes are likely to remain chunky, while ripe red tomatoes will break down almost entirely.
• To test for thickness, spoon a bit of jam onto the chilled plate, return it to the refrigerator and chill for 2 minutes. Drag your finger through it: It should hold its shape on either side without appearing watery or runny. If it's not there yet, continue to cook a few minutes more.
• Remove from heat and discard the chiles de árbol, if using. Divide the jam between jars, leaving 1/4 inch of head space, and seal immediately. Can the jams (see our How to Make Jam guide for more instruction), or store in the refrigerator, using them up within a couple of weeks.