You have two options: You can either choose to bake the tomatoes whole on the stem, or you can slice them in half.
Rinse the tomatoes and put them in a roasting pan lined with baking parchment. Sprinkle with oil, salt and pepper. Add the rosemary springs. Bake at 100°C for 1½ hours.
Slice the tomatoes in half and put them in a saucepan along with the herbs, finely chopped chilli, water, vinegar and sugar. Boil for about 15 minutes over medium heat until the tomatoes are slightly mushy. You can help it along with a handheld blender if you like. Dissolve the cornflour in water and add to the tomatoes. Bring to a boil and cook for 3 minutes until it thickens. Taste it to make sure the starchy flavour has boiled away.
Pour into a jar and let cool.
Serve with Castello Creamy White Chili.