Put the goat cheese into the freezer for 15 mins to make it easier to slice.
Add the oil and the onions to a frying pan and fry for a couple of mins over a high heat. Lower the heat and cook for another 10 minutes.
Add the garlic and peppers to the pan, season with salt and pepper, cover again and soften over a low heat for a further 20 mins until completely soft.
In crease the heat, remove the lid and fry for about 5 mins 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.
To make the base, put the flour, butter, parmesan and mustard powder into a food processor. Season with salt and pepper and whiz until crumbs form. Add the water and whiz again until it comes together to form a dough.
Roll out on a floured piece of non stick baking parchment to a diameter of 11in round. Flute the edge and prick the base with a fork.
Spoon the onion mixture onto the base and spread to within ¾ in of the edge. Arrange the tomatoes and olives on top.
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 mins until the pastry is lightly golden and the base is crisp. Remove the goat cheese from the freezer and cut into 6 slices.
Take the base out of the oven and arrange the cheese on top of the tomatoes. Return to the oven for 5-8 mins or until the cheese has melted. Scatter with parsley and serve hot.