If you want to make ketchup, you don't have to break any tomatoes. This is a way to get all of the delicious ketchup flavors inside the tomatoes!
With the tip of a sharp knife, cut away the stem on each tomato. Push a sugar cube into each tomato. With the tip of the knife, pinch three small holes in the skin, and stick 1 clove, half a bay leave and half a star anise into each tomato.
Place the tomatoes in an ovenproof dish and bake in the oven at 200ºF/90ºC overnight. If you do not have that much time, bake at 300ºF/150ºC for 1 hour and 30 minutes.