Process flour, butter and salt together in a food processor, until the mixture resembles fine breadcrumbs. While food processor is still running, add yolks, then cold water, until a dough just comes together. Form into 6 balls, wrap in cling film and refrigerate for at least an hour.

Heat oil in a saucepan over a low heat. Add onion, thyme, bay leaf and salt. Caramelise, stirring occasionally until soft and golden; this may take up to an hour. Add pepper, discard thyme and bay leaf.

Preheat oven to 180°C. Lightly grease six 10cm-diameter tart cases. Roll out pastry on a lightly floured work surface to 5mm thick. Line cases, pressing firmly into edges and rest in fridge for 30 minutes.

Prick pastry bases with a fork, trim excess around the edges and line with foil and baking weights, like rice or beans. Place on a baking tray and bake for 15 minutes. Remove foil and weights, then bake a few minutes more until crust is golden. Remove from oven.

Process goat's curd, cream cheese and eggs with some seasoning in a food processor until smooth. Divide the onions among each pastry case, then pour the cheese filling to just below the rim. Bake for 12 minutes, or until set.

For the salad, cut tomatoes and place in a large bowl with seasoning, oil and vinegar. Tear basil leaves and mix together with the tomatoes. Marinate at room temperature while tarts are cooking.

Remove the tarts from oven and rest for 15 minutes. Serve with tomato salad.