Preheat the oven to 140 degrees C. Scald the tomatoes in a bowl of boiling water for 30 seconds. Drain well, then refresh under cold running water. Peel off the skins, then cut them into quarters and remove their seeds with the point of a knife.
Pour 1 1/2 tablespoons of the oil onto a large non-stick baking tray and sprinkle with the chopped thyme, sugar and seasoning. Turn the tomatoes in this mixture two or three times, then spread them out in a single layer. Scatter the garlic over the top. Bake for 1 1/2 hours, or until the tomatoes are caramelised. Leave to cool.
Increase the oven temperature to 200 degrees C. Lightly grease the base of four 10cm tart tins. Cut out four circles of pastry, each measuring 10cm in diameter, to fit the tart tins. Spread the tomatoes evenly over the base of the tins. Top the tomatoes with a circle of pastry. Bake for 10 minutes until the pastry is puffed and golden.
Turn the tartlets out, upside down, onto individual plates so that the tomatoes are now on the top with the pastry underneath. Drizzle with the remaining olive oil, season with pepper and serve at once, garnished with fresh thyme.