Start with our step-by-step canning how-to.
Using a vegetable peeler, remove the zest from the lemons in wide strips, leaving the bitter white pith behind. Squeeze the lemon juice through a strainer into a large, wide saucepan. Add the lemon zest, tomatoes, sugar, cumin, 4 teaspoons salt, the red pepper flakes, cinnamon sticks, cloves and ginger. Cook over medium-high heat, stirring occasionally, until the tomatoes are juicy and the sugar dissolves, 15 to 20 minutes. Continue to cook, stirring occasionally, until the tomatoes are dark and syrupy and a candy or deep-fry thermometer registers 220 degrees F, 40 to 50 minutes (the timing may vary depending on the juiciness of the tomatoes). Reduce the heat if the mixture starts to scorch. Discard the cinnamon sticks.
Meanwhile, sterilize four 8-ounce canning jars and lids.
Fill the jars with the tomato mixture, leaving 1/4 inch headspace, then seal and process.
Photograph by Charles Masters
Recipe courtesy Food Network Magazine