2 cups sugar
3 pounds ripe tomatoes, cored and thinly sliced (1/4 inch)
Large pinch salt
Grated zest of 1 lemon
Juice of 1 lemon
1 cinnamon stick
1/2 teaspoon fennel seeds, lightly crushed
2 dried red chiles or 2 tablespoon chili flakes
Pour 1/3 of the sugar over the base of a 12-inch braising pan or other baking dish. Layer half the tomatoes, overlapping the slices, in the pan. Sprinkle with 1/3 cup sugar, and top with the lemon zest, lemon juice, cinnamon stick, fennel seeds, and chiles. Top with the remaining tomatoes, followed by the rest of the sugar. Let sit for 30 minutes. Heat the oven to 400 degrees F.
Place the pan, uncovered in the oven and let cook for 1 hour. The tomato juices should simmer actively. Check every 20 minutes, spooning the juices over the top tomatoes, and removing the chiles if they char.
Continue roasting and checking every 20 minutes — the tomato juices should begin to gel at 2 hours, but it could happen a little sooner or later. Test the juices by spooning a little onto a plate, letting it cool, and running your finger though it. If it holds the line, the jam is ready. Remove the jam from the oven and put it into jars and keep it in the fridge.