Arrange tomatoes, onions and garlic on a baking tray. Bake in a preheated oven at 160°C for 40-45 minutes or until tomatoes are soft and the garlic and onions turn golden.
Skin the onions and garlic and chop coarsely. Halve the tomatoes, then dice. Heat a little olive oil in a saucepan, fry garlic and onions until fragrant. Add the tomatoes to mix. Pour in the fresh chicken stock. Add mint leaves, cracked black pepper, salt and pepper. Bring to a boil, then reduce the heat and simmer for 10-15 minutes.