Preheat the oven to 180C/350F/Gas 4.
Place the puff pastry on a non-stick baking sheet. Prick all over with a fork, leaving a 1inc/2cm border around the edge.
Spread the jar of pesto over the pastry base, being careful not to cover the border. Then lie the tomatoes on top of the pesto, overlapping slightly. Season generously with sea salt and freshly ground black pepper.
Bake in the oven for 15-20 minutes or until the pastry border is crisp and golden and the tomatoes are soft.
Dress the salad with two tbsp of olive oil and the lemon juice, season generously with salt and freshly ground black pepper and mix well.
To serve, cut into the tart into slices. Place the salad in the centre of each serving plate and place a slice of tart on top. Finish with a drizzle of olive oil.