A bouquet garni is a bundle tied together containing spices. If you do not have cheesecloth, try a coffee filter. Do not use a paper towel. It will disintergrate.
Lay the cheesecloth or filter flat. Add the bay leaf, red pepper flakes, and cumin seeds. Gather the sides of the cheesecloth or paper filter, enclosing the spices. Tie up the bundle with the piece of string. Be sure to leave a tail of string so that you can pick up the bundle when the jam has finished cooking.
Making the jam
Add the tomatoes, sliced shallots, sugar, apple cider vinegar, lemon zest and juice, salt, and bouquet garni to a small saucepan. Bring to a boil over medium-high heat. Then lower the heat to let the jam thicken. The tomatoes will start to split and pop. The sugar will thicken as the liquids reduce.
After about 25 minutes, the liquid in the jam should be thick. Do not cook out all the liquid. The tomatoes should be very soft and have lost shape. Remove the bouquet garni. You can squeeze out any liquid by pressing the bundle up against the side of the pan with a spoon.
As the jam cools, it will continue to thicken.
I have estimated a serving to be 2 tablespoons. You can adjust the spice level to your liking by changing the amount of red pepper flakes.