Preheat the oven to gas 6, 200°C, fan 180°C. Roll the pastry out on a lightly floured surface until it is about 5mm (¼ in) thick. Place a 25cm (10in) dinner plate on top as a guide and cut out a circle, then spread evenly with the pesto.
Pour the vinegar into a non-stick, 20cm-base (8in) ovenproof frying pan and scatter the sugar and thyme evenly over the base. Add the tomatoes in a single layer and drape the pastry circle over the top, pesto-side down. Gently tuck in the edges to encase the tomatoes snugly and bake in the oven for 20 minutes, until the pastry is puffed and brown.
Let the tart rest for about 3 minutes then place a large serving dish on top and, wearing oven gloves, carefully flip the whole thing over. Scatter with some more thyme, then serve with salad and some crumbled goat's cheese.
Find out more about our Sugardrop tomatoes