After the brazing dish is taken out of oven shift the oven rack up to 10 cm (4″) from the broiler. Line lightly oiled baking sheet with sliced tomatoes and broil until charred, preferably with fan assist turned on if it is available.
Note:
Watch it carefully to prevent burning, you want it caramelized and not burned! Time will depend on the oven, thickness of tomato slices, distance to the broiler and water content. It took me about 8 minutes.