1. Put the goat cheese into the freezer for 15 minutes to make it easier to slice.
2. Add the oil, garlic and the onions to a frying pan and cook over low heat for approximately 30 minutes, until completely soft.
3. Increase the heat, remove the lid and fry for about 5 minutes until lightly golden. Stir in the vinegar and thyme. Set aside to cool. Heat the oven to 425F and slide in a baking sheet to get hot.
4. Roll out the puff pastry on a floured piece of non stick baking. Flute the edge and prick the base with a fork.
5. Spoon the onion mixture onto the base and spread to within ¾ in of the edge. Arrange the tomatoes and olives on top.
6. Remove the hot baking sheet from the oven and slide the parchment and tart onto it. Return it to the oven and bake for 20-25 minutes until the pastry is lightly golden and the base is crisp. Remove the goat cheese from the freezer and cut into 6 slices.
7. Take the base out of the oven and arrange the cheese on top of the tomatoes. Return to the oven for 5-8 minutes or until the cheese has melted. Scatter with parsley and serve hot.